On a cold Saturday afternoon in January, would you like to . . .

A. Curl up with a good book by the fire.

B. Grab your skates and head to a local ice rink.

C. Put on a bathing suit and jump into the frigid waters of the Chesapeake Bay.

If you chose C, you’re a great candidate for the Maryland State Police’s 18th annual Polar Bear Plunge, to be held Saturday at Sandy Point State Park near Annapolis. Police spokesman Greg Shipley said he expects about 13,000 people — including kids — to brave the cold waters near the Bay Bridge while 10,000 others hold their towels, cheer them on and enjoy the bands, food and festivities at PlungeFest 2014.

“It really is a party on the bay,” says Jason Schriml of Special Olympics Maryland, which expects to receive more than $2 million from sponsors supporting plungers. The money will be used to provide free, year-round sports training and competitions for 6,500 Maryland children and adults with intellectual disabilities.

While plungers are enthusiastic about supporting Special Olympics athletes, they also get a kick out of running into the cold water, especially if they do it with friends.

“Just the fact that you’re with your friends is such a motivation to jump in the water,” said Calli Yancey, a senior at South River High School in Edgewater who plunged two years ago.

Most plungers get in and out of the water as quickly as they can, usually in about 30 seconds. Others run out to a line of 70 water-rescue divers wearing wet suits and standing chest-high in the water. Some plungers high-five one of the divers, and others force themselves to dunk their heads underwater.

Sixteen-year-old Savannah Boyd of Anne Arundel County is a dunker.

“As soon as you go under, you need to get out [of the water] immediately,” said Savannah, who has plunged twice.

The water at Sandy Point hovers around 37 degrees this week. In past years, the water sometimes has been so cold that volunteers had to break through ice and slush before the plunge could begin.

Last year, more than 1,300 of the plungers were between the ages of 11 and 18. Some were even younger: Savannah’s sister, Natalie, was 9 in 2013 when she made her first plunge. As thousands of people rushed in and out of the water, Natalie lost sight of her parents on the beach, but she managed to stay near Savannah.

When she plunges again Saturday, she has a plan. “Now I’m going to know exactly where my parents are,” Natalie said.

Tips for taking the plunge

Wear sturdy shoes. Greg Shipley, who plunges every year, recommends wearing old athletic shoes — the kind with shoelaces — to protect your feet. Flip-flops don’t offer enough protection and might float away in the churning water. Every year volunteers find hundreds of lost shoes after the event.

●Remove your glasses! If possible, leave glasses with a friend or parent on the beach. (If you’re lucky, that person also will be waiting with a towel or blanket when you get out of the water.)

●Wear warm clothes over a swimming suit. Then — as hard as it is — take off everything but your suit before you get into the water. “You’ll get drier and warmer faster if you have fewer clothes and looser clothes,” says Jason Schriml, another experienced plunger.

●Remember why you’re doing this. Adam Hays, a Special Olympics athlete from Frederick, has been plunging for 10 years. “It’s cold, but it only lasts a few seconds or a few minutes, and I’m protected by the love and the warmth of those around me,” he says. “And I know there’s a warm towel waiting for me when I run back out.”

More information: The Maryland State Police Polar Bear Plunge

When: Saturday, 8 a.m. to 5 p.m. A second plunge, called the Cool School Challenge, will be held March 5. It’s just for school teams.

Where: Sandy Point State Park, 1100 East College Parkway, Annapolis.

How old: All ages. There is a Pee Wee Plunge (age 8 and younger) and Family Plunge (for families with children age 12 and younger) at 11 a.m. Permission from a parent or guardian is required for age 17 and younger.

How much: Each plunger must raise at least $75 for Special Olympics. Kids in Family Plunge must raise at least $50.

For more information and forms: A parent can call 410-242-1515, ext. 503, or go to www.plungemd.com.

— Rebecca Jones