Summer months bring swimming, boating and other fun water activities, but police and fire fighters are reminding citizens to be careful.

Rivers are especially hazardous. On Sunday, 33-year-old James C. Bryant of Federal Way drowned while rafting on the Skykomish River.

But mindfulness is important on all bodies of water, rescuers say.

“People overestimate their abilities and underestimate their surroundings,” said Kim Schroeder, a safety education specialist with Snohomish County Fire District 1.

Although air temperatures are rising, surrounding waters are still startlingly cold.

Everett already has seen an 85-degree day, on May 1, but water temperatures remain in the low- to mid-50s, according to the National Oceanic and Atmospheric Administration.

“The air temperature is warm and you may be hot and sweaty on the beach, but the water 12 hours ago was snow,” said Snohomish County sheriff’s Lt. Rodney Rochon, who leads the marine unit. Hypothermia alone can be fatal, and it can also lead to drowning.

Bryant died from heart problems related to cold-water exposure, according to the county medical examiner’s office.

Last year, at least 10 people drowned in Snohomish County.

When it comes to swimming, rivers should be avoided entirely.

“There are more drownings on the river than anywhere else,” said Sgt. Jeff Hendrickson of the Everett Police Department’s marine unit.

According to Trent Nunemaker, who is with the hovercraft rescue team of Fire District 19 in the north county, those who are not familiar with the area and local bodies of water could be in serious danger.

“People from out of town who float the Stillaguamish River sometimes don’t realize how long it will take to float the river,” said Nunemaker. “The river gets really lazy during the summer and we have to rescue those people who didn’t realize the length of the river. We usually pick them up halfway through their planned route around 10 p.m.”

Rivers might look calm on the surface, but beneath the surface are a variety of rocks and debris that can endanger even the strongest swimmers.

On rivers, lakes and Puget Sound, Rochon urges boaters to ensure their engine’s battery is fully charged. Hulls should be inspected for leaks and equipment should be tested before going on the water.

Rochon also warns boaters to be cautious even in familiar waters.

“The water over winter has done a lot of things,” said Rochon. “Where it was safe last year may not be safe this year.”

Except for those born before 1955, a boater safety card is mandatory in Washington. For more information, go to www.boatered.org.

Wearable life vests also are mandatory for every passenger on board. Children under 12 must wear one when the boat is in motion. Adults should take care to make sure that children are properly fitted. A life jacket that is too large could drown a child.

Last Friday, Life Jacket Loaner Cabinets opened at a variety of locations throughout Snohomish County. The cabinets are open from Memorial Day weekend to the end of Labor Day weekend. Fire departments in Snohomish County are collecting gently used life jackets throughout the summer and donating them to Safe Kids Snohomish County, which runs the loaner program.

An adult should be watching children at all times. Avoid activities such as talking on a cell phone, reading and other distractions while supervising a swimming child.

“Supervision is key, said Shawneri Guzman, who works in trauma and injury prevention at Providence Regional Medical Everett and is a coordinator for Safe Kids Snohomish County. “Life jackets are not babysitters.”

Water safety tips

For more information about boater education, go to www.boatered.org.

For child safety and life jacket rental information, go to www.snosafekids.org. Life jacket rental cabinets are located at local parks.

Never use inner tubes and rafts designed for swimming pools on open water.

Know your limits; do not attempt a section of river beyond your skill level.

Pay attention to weather and water conditions. If the water temperature and air temperature combined total 100 degrees or less, wear protective clothing.

Enter cold water slowly.

Avoid swimming near boat ramps or in boating areas.

Avoid downed trees, snags and confluences.

If your vessel capsizes, float on your back, feet together and pointed downstream. If you go over a ledge or drop, tuck into a ball.

If you’re caught in a fast-flowing river or rapids, try to float feet first in a half-sitting position. Release your craft only if it improves your safety. Stay upstream, away from the boat.

Also this time of year, emergency crews often have to respond to incidents where infants or toddlers have fallen out of windows, according to Snohomish County Fire District 1. Parents should move furniture away from windows and consider installing safety devices. Screens will not bear a child’s weight. Window devices should be easily removed by adults in case of a fire.