There’s a reason people flock to the ocean when it’s hot. Submerging in cool water draws heat from your body at a rapid rate and lowers your core temperature. That’s great if you’re taking a quick dip to cool off, not so great when you’re 30 feet below the surface trying to appreciate the parrotfish.
Feeling too cold not only wrecks the enjoyment of your dive, it also can be dangerous. As your core body temperature declines, so does your reaction time and thought process. Your body also uses more energy to keep warm, so you have less endurance for your dive. Here’s how to hold onto your body heat and enjoy your dive.
1. Cover your head. You wouldn’t go skiing without a hat; don’t go diving in cold waters without a hood. It should be the first piece of thermal protection you consider. While near-surface blood vessels elsewhere in your body close down to minimize heat loss, those in your head continue at full flow.
2. Keep the water out. The best wetsuit or dry suit is worthless if it lets in too much cold water. Repair broken zippers and split seams. Pay special attention to the collar seal because as you swim forward it can act as a channel for water. A hood can pull double duty keeping your head warm and sealing the neck opening.
3. Bare nothing. Heat loss is huge where cold water flows over bare skin, so a thin full-length suit is warmer than a thicker shorty.
4. Stick to shallow waters. The deeper you dive, the more the insulating neoprene of your wetsuit compresses—effectively making it thinner and less insulating. Breathing air under less pressure also chills you less.
5. Surface if you shiver. Uncontrollable shivering is a warning sign of hypothermia.
6. Wrap up on deck. On deck, your wetsuit effectively becomes a swamp cooler as you sit there in the sea breeze. Many divers actually lose more heat between dives than when in the water. Wear a parka or a windbreaker, or take off the suit and dry off.
7. Have a hot drink. A thermos of hot cocoa can help warm your core between dives. Just steer clear of the spiked variety, as alcohol sends blood to your skin’s surface making you lose more heat.