Anybody who dives into Lake Tahoe this Memorial Day weekend better prepare for a polar plunge — the water is frigid.

That clear, blue water may look friendly and inviting when the sun is shining, but in a matter of seconds, it can turn deadly. It's a great time celebrating the long holiday weekend in one of the most beautiful places on the planet, but it's not time to forget how dangerous these world-class surroundings can be.

Jumping right into Lake Tahoe this weekend can be one of the most dangerous. The body could go through a cold shock response that causes an involuntary gasp reflex caused by sudden immersion in cold water, and if it happens underwater, drowning can happen in a matter of seconds.

"The water is cold — everybody should be wearing life vests or PFDs (personal flotation device)," said Karl Koeppen, battalion chief for South Lake Tahoe Fire Rescue. "We already had a canoe capsize last week, a Tahoe native, luckily he made it. But even the locals aren't used to this water. It just takes a second. It takes your breath away and it happens fast. The muscles lock up and your first reaction is to take a breath, and it's not there."

Being in the best physical shape may not help avoid cold water shock; it may even hurt not having a layer of fat. A San Jose Earthquakes professional soccer player last year nearly drowned at Zephyr Cove Resort. The cold water caused his body to go into shock about 20 yards from shore and he went under after yelling for help.

"This is frequent with athletes who don't have a lot of insulation or fat," Eric Guevin, Tahoe Douglas Fire Protection District fire marshal said last year when it happened. "It is a point where they lose the control of their body and their muscles."

When responders arrived, teammates and a bystander had rescued the player but he drifted into a coma. He fortunately emerged a couple days later.

The cold water is just one of the dangers to be mindful of this weekend while recreating in the water.

The weather Saturday may not be ideal for fun on the water, but the sun will come out in force Sunday and Monday with highs in the mid 70s. While the temperature will be warm, the water won't be.

Koeppen said the wind may pick up at any time and for people in canoes, kayaks or paddleboards, they must be especially aware of the conditions.

"People need to be careful not to go out too far," Koeppen said. "You never know when that wind could pick up and take you right out into the middle of the lake."

Koeppen said people getting hit by propellers also posed a problem last year. He said SLT Fire Recuse responded to three or four serious incidents.

"When people leave the craft and go into the water, the engine should be cut," Koeppen said.

Boaters should always be prepared for an accidental fall overboard, which is one of the most common fatal accidents every year at Lake Tahoe.

And, of course, Koeppen says maybe the single most important piece of equipment to use on the lake is a "save your" life vest or personal flotation device.

"Boaters and swimmers need to watch for other boats and everybody should be wearing life vests," Koeppen said.

Koeppen said South Lake Tahoe Fire Rescue has a new boat that will be available to respond 24 hours a day, seven days a week. It's the only around-the-clock responder on the south side of the lake. The coast guard on the North Shore can respond 24/7.

Some tips to stay safe on Lake Tahoe include never swim alone, relay your plan to a friend before you go, check the weather conditions, know your swimming limitations and don't operate a boat under the influence of drugs or alcohol.

Boaters are required to carry life vests for every person on board, including paddleboards, kayaks and rafts. Children under 13 are required to wear a life jacket on a boat at all times, unless in an enclosed cabin.