In warm weather, many people seek cooling relief in ponds, rivers, oceans, pools, and other sources of water. Swimming is a popular warm-weather activity, but it can quickly turn deadly if swimmers are not careful in the water.

The U.S. Centers for Disease Control and Prevention warns that, between the years of 2005 and 2014, an average of 10 deaths per day in the United States were attributed to unintentional drownings unrelated to boating. About one in five people who die from drowning are children age 14 and younger. The World Health Organizations says drowning is the third-leading cause of unintentional injury death worldwide.

Drowning is a concern when in the water, but it’s not the only potential hazard.

Harmful algae blooms

Algae are plant-like species that are found all over the planet. Algae inhabit different bodies of water and can be important food sources for marine life. The CDC notes that, in certain circumstances, an overgrowth of algae may overpower water sources. Not all algae are harmful, but some blooms will produce toxins that can be dangerous to people and animals. Such algae may lower levels of oxygen in the water, killing plants and animals. Individuals are urged to avoid areas with harmful algae blooms and restrict fishing for food consumption during times of blooms.

Shorebreak

The National Ocean Services says a shorebreak is an ocean condition in which waves break directly on the shore. The power of these waves can cause injuries to the body, potentially hurting the spines of people who dive headfirst into the break. Others may be knocked over by waves and suffer injuries as a result. Swimmers should observe waves and ask a lifeguard about conditions before going into the water.

Jellyfish

Sharks elicit fear among many ocean swimmers, but smaller animals can be dangerous as well. Most jellyfish can sting, but not all have venom that hurts humans, says the National Oceanic and Atmospheric Administration. Around 70 species of jellies can harm or occasionally kill people. Ocean swimmers should take note of jellyfish postings at the beach and examine the sand as well. Wet tentacles can still sting, even on washed-up jellyfish.

Unsupervised activity

It’s essential that swimmers exercise caution around any body of water. Because water can be unpredictable, it’s always best to swim with a friend and stick to areas protected by lifeguards. The Red Cross suggests preventing unsupervised access to water structures and maintain constant supervision whenever kids are around the water – even if lifeguards are present. Adults should avoid distractions and alcohol when supervising kids.