Open Water 101: Marine Dangers and How Best to Cope With Them

In ancient times, mariners dreaded venturing too far from the shoreline for fear of the lurking monsters at the edge of the then-known universe. Although the beasties and creatures they imagined have been largely proven mythical, there are still some hazards in the open water—even close to shore—that can ruin a nice swim.

If you’re swimming in the ocean, there are a whole range of hazards related to water conditions that you need to be aware of before you get started. Here’s a quick overview of the most common conditions (and critters) that pose a threat to ocean swimmers.

1. Rip currents. Rip currents are columns of water movement that begin at the shoreline and extend perpendicular to the beach for anywhere from a few yards to a quarter of a mile or more. They can suck a swimmer out well past the intended swimming place and can be very scary to experience. Rips result from bumpy silt and sand at the bottom and the surging surf rolling across that uneven terrain. If you’re trapped in a rip, ride it out until you feel it weaken. Then, swim parallel to shore until you are completely free of its tug—you’ll know it when you feel it. Then, you can turn and swim directly into shore well away from the rip. The swimmer will always lose in a fight against a rip current, so better to ride it out before trying to return to shore.
2. Tidal changes. In 2004, 19 Chinese migrant clam diggers died when a rushing, incoming springtide closed in around them in Morecambe Bay, England. Caught unawares and unable to outrun the quickly rising surf, most of the workers in the group drowned while rescue teams attempted to save those who were able to cling to what little higher ground they could find in the tidal flats. Most places in the United States do not have such a quick and dramatic turn of tide, but impending storms, seasonal fluctuations, and moon phases can all affect the timing, speed, and height of tide cycles. Know the area before you head into the water. Local fishermen are usually the best source of this kind of information, so head to the docks and ask around.
3. Currents. Similarly to tidal changes, currents are a uniquely local phenomenon and fishermen and boaters familiar with the waters you’ll be venturing in to can be your best source of information regarding timing your swims. Knowing which way the current is running can make or break your swim, as swimming directly into a strong current is often nearly impossible, if not exhausting and slow-going. Understanding local currents and timing is critical to planning an effective training swim or event, so learn the water and how it moves before you start.
4. Surf and chop. General water conditions on any given day can change dramatically from minute to minute and pose a risk to your swim. Along the shoreline is one danger zone you need to learn about. Especially at high tide, a sharp drop off of sand at the high water mark can result in a difficult shore break that can make entering and exiting the water downright treacherous. Farther out, wind, sandbars, and uneven bottom conditions can stir up chop, which can make you feel like you’re trying to hold a straight line inside a washing machine. Although that can be great practice for conditions you may be dealt in the English Channel, for example, it’s seldom fun to be tossed around. Prepare for the unexpected and be ready for anything the ocean may throw at you on any given day.
5. Water temperature. Like Goldilocks, us open water swimmers need the water to be in that sweet, “just right range,” which for most adults falls somewhere between 65 and 80 degrees. Go much warmer, and you risk heat stroke, hyperthermia, and dangerous complications from overexertion in too-warm water. Go much colder, and you risk hypothermia, a potentially lethal condition that can sneak up quickly. Find out what your most comfortable temperature is, and if the water is far away from that point, enter with caution. If the water is cold, a wetsuit may help. If the water is very warm, skipping the swim altogether might be the safer option.
6. Critters. These days, jellyfish and sea lice are everywhere, thanks to lots of factors, not least of which are climate change and overfishing of these animals’ natural predators. For most open ocean swimmers, jellyfish and sea lice are likely to be the worst of the sea life they will interact with, but it’s not impossible to encounter other animals running the gamut from sea lions and rays, to skates, turtles, and yes, even sharks. Jellyfish and sea lice notwithstanding (their invertebrate forms do not wish us ill-intent, their stinging cells simply fire when they feel us near) most sea life wants nothing to do with us. If you do see something, steer clear. Most animals will not attack unless provoked, so the best defense is to just leave them alone and swim on or leave the water.

For more on additional hazards you may face in open water, see the second part of this article, Here Be Dragons, Part II.