Their breath freezes, their bedroom sways and sometimes, their pets fall into the icy water.
But for people who live aboard their boats year-round, there's no place to be in the winter but afloat.
"It's a lot of bliss," said John Benson, who lives aboard a 42-foot sailboat at tiny Port Williams marina on Back Creek in Annapolis. "To me, it's a tremendous sense of knowing I'm in the right place."
Mr. Benson, 36, is one of scores of "live-aboards" who don't flee for the warmth of a fireplace after the last cruise of the summer. Instead, he bundles up and waits out the winter.
He and other live-aboards on boats with names such as Avenger and Rio, are tucked away in marinas along the Chesapeake Bay, hidden behind sealed-up sailboats and plastic-wrapped yachts. And they are steeling themselves for spring, when the quiet docks fill once again with boaters.
"It's nice in the winter because it's very private," said Jan Kanner. "Most of the slip tenants are not here. In the spring, when they start coming back, you feel you're being invaded." Ms. Kanner and her husband, Gary, have lived aboard their 41-foot sailboat at Port Annapolis Marina with their dog, Teak, for seven years.
While it's unclear how many live-aboards reside in Maryland -- the government does not keep such records -- Timothy Murray, publisher of Living Aboard magazine, estimated the population at several thousand.
Living aboard is not cheap. Slip rentals cost roughly $3,500 a year, and that doesn't include utilities or payments on boat loans. Nor is the lifestyle as rare as it was 30 years ago when live-aboards were considered dreamers and adventurers.
These days, most live-aboards are mainstream and well-to-do with lots of links to the land. Some work in Washington or Baltimore. Others entertain their grandchildren on their boats on weekends.
But it takes an unusual type to live on the water in winter, whether the season is marked by a few days of single-digit temperatures or steady blasts of ice and snow.
Staying warm is the first challenge. While live-aboards say it is merely unpleasant to back into a cold, metal mast before getting dressed, it is downright dangerous for the machinery to get too chilly. Pipes can freeze, burst and flood the boat. And when a winter storm blows through, there is no buffer.
"I know I have to turn up the heat if I can see my breath," said Phil Aylestock, who moved aboard his 43-foot wooden sailboat at Bert Jabin's Yacht Yard on Back Creek in Annapolis four years ago.
"The big thing is, it's not like a house where you can ignore it for a while," said Mr. Aylestock, 45. "You're constantly aware if it's freezing, if the lines are chafing, if the wind changes direction."
But not all of live-aboards stick it out during the worst weather. "When it's real cold, I call a friend and say, 'Can you take an old dog in at night?'" said Richard C. O'Connell Jr., 64, whose 30-foot catamaran is docked at Anchorage Marina in Fells Point.
Most boats are equipped with small, space heaters that keep the narrow cabins warm. Marina owners charge for the electricity, which is supplied to the vessels from power lines ashore.
For the most part, live-aboards savor the pared-down existence that is enforced by the cramped living space.
"There is a certain freedom from possessions," said Paul Winston, 63, an artist who lived with his wife, Patty, in New York City for 37 years before moving aboard their boat at Port Annapolis three years ago.
"You realize you are owned by the things you own," he said.
But exposing a settled, urban life to the elements has its hazards.
On cold winter days, the Winstons won't allow their cat, Felix, to climb on deck because he occasionally falls over the side. Felix, who also gets seasick, spends most of his days on various cushions in the cabin.
And the dangers aren't relegated to pets.
Last month, Marsha Gohsman was boarding her sailboat with her arms full of shopping bags. She missed the boat and clung to the side while half of her dangled in Back Creek. Finally, she climbed onto a pier and took a hot shower, unharmed and grateful.
The Winstons' neighbors, Rob and Lisa Sarini, haven't made any disastrous slips in five years as live-aboards. But they worry. So Mrs. Sarini watches her husband when he walks the dog on the docks on icy nights. She keeps an emergency whistle nearby and the boat's loudspeaker activated in case he falls in, Mr. Sarini said.
Live-aboards say the rewards are worth the trials of winter.
"I'm the first person in my family with waterfront property," Mr. Benson said. "I feel like a millionaire."
Mr. Sarini, 38, said he and his wife "were bored, and we had to leave" their home in Burke, Va. "Why not live on a boat?" he asked.
The Sarinis still order pizza and watch movies on cable, but they also watch the sun set over the water every night. They must forgo some modern conveniences, however.
Live-aboards ration their water during winter because the lines that feed boats during summer are shut off. On many chilly mornings, live-aboards can be spotted scuttling across the docks in flip-flops and sweat pants to get to showers operated by the marinas.
Boaters must pump out their sewage holding tanks and handle their household garbage with care.
Some live-aboards get homesick for their old possessions, from books to bedroom sets to baby grand pianos. But in most cases, live-aboards say they are trying to get rid of the clutter and lead a more simple life. The long winter affords them a kind of seclusion they rarely find the rest of the year, and sometimes that's not even enough, they say.
Some boaters will close a curtain or light a particular porthole as a sign to their neighbors they don't want to be disturbed.
Mr. Benson is one of eight single men living aboard boats at Port Williams Marina. But this is not the stereotyped swinging singles scene. Mr. Benson reads most nights and plays with his basset hound, Bullet.
"It's so quiet," he said, "you feel like you can hear the blood going through your veins."
For Mr. Benson, the peace is one of the best things about his home. That, and another feature, he said:
"When you want to go away, you never have to pack."