Factors that Affect Diving

As divers, the ocean is our second home, playground and refuge from the trappings of the everyday world. When everything aligns just so and conditions are right, being in the ocean can be a magical and energizing experience. The more time we spend under the surface, the more at home we feel, and the more we learn to tune into the oceans many patterns and moods. The ocean can be gentle, calm and playful, but can turn in a moment to angry, violent and dangerous. Understanding this, and developing a deep respect for this environment is of paramount importance for anyone who chooses to spend time here. To better your understanding, it is good to be aware of some of the basic factors that can affect a dive.

Wind, Waves, Tides and Currents

These four things, more than any other, have the potential to make or break a dive because of the dramatic effect they can have on conditions both above and below the surface. Due to their importance, we will cover these topics in greater detail in another post, but here we will provide a basic overview.  

Watch this video on Beginner’s Guide to Monterey Bay Dive Conditions

Photo by Viktor Klinger

Wind can have a dramatic effect on the conditions you will experience while spearfishing. Wind generates waves, both in the form of long period “groundswell” and short period “wind swell”, both of which come with their own set of challenges. Wind can create local surface currents that present hazards to divers, and deposit dirt and sand into nearshore waters, affecting visibility. Wind can also be your friend. Breezy conditions create a slight chop that diffuses light penetrating the surface, which can increase fish activity. Surface currents created by wind can also spur feeding behavior in predatory fish species. Sustained offshore winds (wind that blows from land toward the ocean) can drive murky surface waters away from the shoreline and bring clear, clean water from the depths—a mechanism known as “upwelling”. Sustained onshores can do the exact opposite—creating choppy surface conditions and stirring up sediment along the shoreline, which will quickly turn good visibility into murk. This is why getting to know your local dive spots and how the wind will affect them is so important. 

All waves are generated by wind, beginning as storms that can occur locally or far away. The wavelength or “period” and the direction the waves originate from have the most potential to affect the diving conditions on any given day in a particular spot. Large, offshore storms that release tons of energy into the ocean generate powerful groundswells which travel thousands of miles before crashing onto reefs and shorelines. These types of waves present an obvious challenge to divers because they are big, powerful and potentially deadly. A cove that is normally calm and flat during most conditions can become a violent washing machine if large swells enter from the right direction. Alternatively, even if there is a big swell hitting up and down the coastline, it may be that there are certain areas which face away from the swell and provide enough shelter to create safe diving conditions—another reason why getting to know your dive locations well is so important. Long period swell also causes surge, which is a diver’s term for wave energy transforming into water movement as it makes contact with the sea floor. It is important to understand that the longer the period (the amount of time that occurring between 2 swells passing a given point), the deeper the surge will reach, and the stronger it will feel. This can be dangerous when diving in rocky areas or through kelp, as the water movement will push you quickly.

Local storms generally cause wind swell which makes waves that travel quickly along the surface and create choppy conditions. While wind swells are not as powerful as groundswells, they have just as much potential to develop hazardous diving conditions. Wind swells can pound a shoreline relentlessly, making entry near impossible and destroying the visibility. The chop generated by wind swell can make it difficult to see dive partners and boats. When dealing with wind and swell, it is always advisable to dive with an experienced partner who knows the area or gather advice from a local dive shop before exploring a new place. In general, calm wind and sea conditions are most favorable for diving.

Tides are a third major factor that you will experience in the ocean environment. Have you ever been to a rocky stretch of coastline that was submerged when you arrived, only to be left high and dry a few hours later? This is the effect of tides on nearshore waters—the rising and falling of the ocean in relation to the gravitational pull of the moon. High tide is when the ocean rises to its peak along the shoreline, and low tide is when it recedes away. Typically every day there are two highs and two lows, with the “peak” being when the tide is at its highest point and the “low” at its lowest. The water will be rising or falling the fastest in between the peak and the low, with little to no movement at the two extremes. Learning how to read a tide chart and checking the tides before planning a dive will aid you in finding fish while helping you predict currents and hazardous conditions.

Photo by Joe Platko

Rising and falling tides create currents as the water moves in and out along the shoreline and these currents can coincide with fish activity. It is important to note that while currents can be helpful for finding fish, swift currents moving out to sea or along the shoreline can be very dangerous. When dealing with current it is always advisable to determine the speed and direction before entering the water and plan your dive accordingly. One trick we use in Northern California is to gauge the direction and angle of a bull kelp stalk. You can quickly tell the direction and strength of the current and water movement by observing the nearby marine plant life.

Just like wind and waves, tides and their corresponding currents will affect local dive sites differently. It is particularly dangerous to dive a spot with high current if you can’t easily get back to land down current. We often dive Big Sur, which is a steep and rocky coast line with very few entry and exit points. If you get swept too far in a direction by current, you may not be able to exit the water for many miles. Researching beforehand, diving with knowledgeable buddies and keeping a log of your outings will all go a long way towards puzzling out how these factors align in any given spot to create the conditions for epic spearfishing.

Visibility

We’ve touched on visibility briefly in the previous discussion, but what is it? Visibility is simply how well you can see under the water and is generally referenced by divers in measurements of distance. For example, good visibility in the Monterey, CA region might exceed 60 feet on an exceptional day, while poor ocean conditions can create visibility of five feet or less. It goes without saying that the most pleasurable days to dive and hunt are days when the ocean is calm and clear, but we can not always be so lucky. Every region in the world has different standards for when visibility is acceptable, and when it is best, and safest to stay home. Let’s discuss some of the factors that can lead to good or bad visibility.

The main things that can make or break visibility are waves, wind, tides, runoff after a heavy rain or from a river and organic matter such as algae or aquatic plant life. Generally, large waves and high winds create poor visibility—especially in nearshore zones—while calm surface conditions offer a better bet of good visibility. The wind and swell directions can also play a major role. Wind or waves traveling directly towards shore will almost always negatively affect the visibility, while offshore wind or wind and waves traveling along the shoreline will have less of an impact. Rising tides bring clean ocean water up from the depths and help clear things up, while a falling tide drags debris and sediment into nearshore waters. Algae blooms can last from days to weeks and sometimes drop the visibility to near zero. They can be fairly unpredictable, and it is best to avoid diving until they clear up. Aquatic plants such as kelp can also have a seasonal effect on visibility. In California, long, hot summer days cause kelp to overgrow and die off on the surface, filling the nearby waters with rotting kelp particles. These conditions persist until offshore winds or large fall storms carry the dead kelp particles away from shore. Rainstorms and runoff can also muddy up otherwise clear ocean waters. For health-related reasons, it is recommended not to dive or swim near river mouths, harbors, or outlets for several days after heavy rains, but storms also make for terrible visibility which can last for weeks if there is enough runoff. 

Knowing how these factors play a role in your local dive spots will help you determine when and where to spend your time, but it is understandable that most divers don’t always have the luxury of only going out when conditions are optimal. Therefore, it is important to know what to expect when going spearfishing in good or bad visibility.

Good visibility is, of course, the preferred diving condition. When visibility is prime, the ocean is an incredible place to be. Good visibility makes many things easier. Most divers feel more comfortable and can dive deeper when the visibility is good. Fish and structure can be spotted from the surface, which makes good visibility an excellent choice for scouting new territory. Being able to clearly see your dive buddy for the entirety of their dive makes things much safer. However, these advantages come with their own challenges. A false sense of security can cause divers to push their limits too hard and end up in dangerous situations. Clear waters can make game fish spooky and skittish, necessitating careful stalking and hunting techniques to get close enough for a good shot (read more about hunting techniques here). In these epic conditions it is easy to become distracted by the beauty of the ocean and the fun of the dive, making it even more important to stay vigilant. Keep a close eye on your dive buddy and be aware that the ocean can be unpredictable no matter how amazing the conditions are.

Bad visibility, in contrast, makes almost everything more difficult. While depending on where you are in the world, you might develop a tolerance to low visibility diving based on the average local conditions, I have never met a diver that prefers it. Most divers are less comfortable in low visibility, which can have a dramatic effect on their diving depth and time on the bottom. In either case, poor visibility conditions are not the time to push one’s limits. In bad visibility it is important to stay very close to your partner and ideally dive with a brightly colored float line attached to your gun so that your partner can track your movements when you are down. We at Fin + Forage recommend hunting with a float line anytime that you cannot see the structure on the bottom. In the Monterey region, these float lines have become somewhat of a staple for spearfishers. Not only do they help us stay on top of our buddy, but they come in handy for marking holes and structure on the bottom when we have to swim to the surface for a breath. The only advantage low visibility sometimes offers is that it can make it easier to get close to certain types of fish that would otherwise be difficult to approach. For this reason, spearfishers often use shorter guns in poor visibility and longer guns with more range when visibility is prime.

Plant and Animal Life

Photo by Joe Platko

The ocean is full of wonderful, exotic creatures that are fascinating to view and interact with, but it is important to be aware that some of these creatures can be dangerous to humans. It is always advisable to avoid touching or provoking any sea creature you don’t plan on hunting and familiarize yourself with the local flora and fauna before going into the ocean. Agitating wildlife can be damaging to their health or cause certain species to abandon their habitat. It is best to keep your distance from obvious wildlife such as large marine mammals and sharks, even leaving the area entirely if it is possible. While otters appear cute, they can be very aggressive. Harbor seals are adorable, but have been known to pull off fins under water. A giant Pacific octopus can very easily drown you. Sea lions can be territorial and have even ripped fish off belt stringers. Torpedo rays are electric and can deliver a shock that has been described as being hit by a baseball bat. Corals, urchins, jellyfish and various other stinging or venomous organisms can be equally hazardous. Even plant life can present its dangers. Kelp entanglement is a real threat, and one should always use extra caution when diving around kelp forests or similar plant life. 

Man-Made Dangers

Shipwrecks, oil rigs, buoys, F.A.D.’s and other man-made structures can be exciting places to dive and are generally fish magnets, but they can also be extremely dangerous. It is always important when diving in these types of places to be very aware of any lines, wires, sharp, broken or rusted pieces of metal and all overhead structures during your dive. Dive with a buddy you have a solid relationship with, and discuss your dive plan beforehand so that you both are aware of the risks and paying complete attention while the other is down. Entering into enclosed spaces such as the hull of a boat or the cross beams beneath an oil rig is never advisable under any circumstances. 

Even when diving in natural environments it is important to be on the lookout for man-made hazards. Nets, old fishing line and other debris can attach themselves almost anywhere and present a deadly entanglement risk. 

Above all, one of the most dangerous and potentially deadly man-made hazards you will encounter in the water are boats. Always be aware of your surroundings for the entirety of your dive and be looking and listening for boats in the area. Keep a “diver down flag” in your kit and make sure it is visible above the surface while you are diving. Brightly colored spearfishing floats are also helpful tools that can let boaters know where you are. Understand that these are no substitute for caution and awareness in the water. Boaters may not see your flag or float, they may not know what it means, or worse they may be ignorant of boating safety rules. The best thing you can do is avoid diving in areas with heavy boat traffic, dive early or late when boaters are less likely to be on the water, and exit the water if boat traffic becomes dangerous. 

Vigilant Enjoyment

It may seem like we’ve created a list of all the potential hazards in the ocean to scare would-be divers away, but we are really inviting you to jump in with the understanding that the ocean can be unpredictable and dangerous, and demands our respect. By familiarizing yourself with the hazards and always remaining vigilant, you will be able to enjoy the ocean to its fullest while staying as safe as possible.