How to Check Your Buoyancy for Snorkeling and Skin Diving

One of the most critical things you must do to be successful as a skin diver is to learn how to check and adjust your buoyancy. If you don't wear enough weight, you will be "positively buoyant" and find that it is difficult or impossible to dive underwater. You can't sink or dive if you are positively buoyant.

If you wear too much weight you will be "negatively buoyant" which will make it a struggle for you to swim and rest easily on the surface. This can be exhausting if you don't do something to correct the situation.

The personal buoyancy of your body, your dive suit, and all of the rest of your equipment will affect your buoyancy in the water. Ideally, you will want to be either "neutrally buoyant" or just slightly "positively buoyant."

The big question is, how much weight do you need? If you're wearing a thin, tropical wetsuit (1/8 inch thick neoprene), start with 4% of your body weight. If you weigh 165 pounds, you would start out by wearing six pounds of weight.

For divers wearing a full cold water wetsuit, made from ¼ inch thick neoprene, start with 8% of your body weight. This may be a bit on the light side for some people, but it is better to be too light than too heavy.

To test your buoyancy, enter the water wearing all your equipment, in a location where you can reach out and touch the dive boat or surface float. Have extra weights available on the boat or shore to add to your belt if you need them, but always start your tests with the minimum amount of weight.

The water should be just deep enough so that your fins don't touch the bottom. With your snorkel in your mouth, and your body hanging vertically in the water, take a big deep breath and relax. Don't kick or use your arms to maintain your position. See where you float.

If you float with your eyes right at the surface of the water, theoretically, you are perfectly weighted. If you start to sink you are too heavily weighted and must remove some weight. Kick back to the surface, exit the water, and adjust your weights. If you float with your whole head out of the water, you are too light and should add weight a pound at a time and test again until you have exactly the right amount of weight. It is better to be just a bit "light" than to be too heavily weighted.

You can run the same buoyancy test even if you aren't wearing a wetsuit, but you probably won't need to wear more than four pounds of weight. However, some people are especially buoyant and may need more weight. Take your time and experiment. Just be sure to add only one pound of weight at a time.

Remember that any time that you add accessories they will change your buoyancy. For example, most underwater cameras, dive lights, and spear guns are negatively buoyant and will sink to the bottom on their own. When you carry these items while diving it's like carrying more weights.

It's also important to know that when you are wearing a wetsuit, as you dive deeper, the suit will compress and you will lose buoyancy. This will change your buoyancy underwater, even at a depth of 15 feet. If you dive deep enough, the compression of your suit and the resulting negative buoyancy can make it a real struggle to get back to the surface. In a situation like this, your only option may be to drop your weight belt in order to get back to the top.

Never wear any more weight than you absolutely must to dive. As your wetsuit is used it will gradually lose some of its buoyancy and over time, you will need to remove some of the weight from your belt. If you lose or gain a few pounds this will also affect your buoyancy. If you buy a new wetsuit its buoyancy will probably be different from the suit you owned previously. Check your buoyancy periodically to make sure it hasn't changed.