One of the best things about summer is time spent poolside, lakeside, at the beach or in a boat. Water activities are fun, refreshing and can be great exercise. But drowning, even for the seasoned water-goer, is a very real danger. We know this—it’s the first thing we learn when we hit the water. But what many of us don't learn about is secondary drowning and dry drowning.

Secondary drowning can happen after a person has a drowning experience. After he has been rescued and seems to be fine, water can still be in his lungs. This fluid builds up and then, maybe an hour later, the victim will start to have trouble breathing, as if he is drowning.

Dry drowning results from a person inhaling small amounts of water during a struggle. This can cause the muscles in his airway to spasm, making breathing difficult.

If you’re with someone who has inhaled water, keep an eye out for breathing trouble, chest pain or coughing. The victim may also experience sudden changes in behavior or extreme fatigue. If symptoms are present, even hours later, head to the emergency room.

Fortunately, incidents of secondary and dry drowning are not common. They make up only 1 to 2 percent of drownings a year. But they do happen, and we need to know how to watch for them if we ever find ourselves in a situation that involves a drowning incident or someone who has struggled in the water.