MADISON, Wis. -- Hundreds turned out on Saturday to jump into the frigid waters of Lake Monona or to support those taking the plunge.

Well more than 100 groups registered to participate in the 2007 Polar Plunge in Madison, a fundraising effort benefiting Special Olympics Wisconsin.

Participants collect pledges and plunge into freezing lakes around Wisconsin. There are nine Polar Plunges scheduled around the state this year, and all proceeds collected by plungers benefit Special Olympics athletes in their areas.

School buses running as shuttles transported many plungers to a drop-off point at Olin Turville Park, where the line for registration was frequently long and some had some participants waiting in line around 40 minutes to register.

There were heated changing tents set up, as well as a warming tent and concessions. As participants prepared for their plunge, there was a sense of excitement and nervousness as groups gathered and huddled in the warming tent.

As music played from speakers at the lake's edge, an announcer moved the event along at an efficient pace, announcing each team as the groups cycled down to the jumping platform and then quickly into waiting hot tubs and warming tents after taking the plunge.

"I've got cold feet," said Kate Nast, a grad student in the La Follette School of Public Affairs at University of Wisconsin-Madison and captain of the Fightin' Bobs Polar Plunge Team, as the team's jump time approached. "I got a lot of sleep last night. I've been drinking some hot chocolate and heating up in the warming tent, and now I'm just letting it all go."

There was a wide variety of participants Saturday, with teams ranging from fraternities and sororities to local businesses, schools and groups like Mad Rollin Dolls and the Teaching Assistants Association. Some teams wore costumes.

The Madison Fire Department rescue team was on hand by the jumping platform to monitor the situation.

After taking the plunge and changing in the warming tent, Nast said the plunge itself was unpleasant but that she's happy she did it to support a good cause.

"(The water) was horrible. It was definitely worse than I imagined, and the lake water was gross," she said. "But I've mostly warmed up now and I'm feeling pretty good."

Nast said that she is glad she participated and said she would probably do it again.

"It was paralyzing cold -- and smelly," said UW-Madison grad student Alexis MacDonald, a member of Fightin' Bobs Polar Plunge Team.

Despite that, MacDonald said she would also go through it all again.

Event coordinators put nets under the hole in the lake that plungers jump into so that if anyone were to pass out underwater, they wouldn't be swept out into the lake.

After plungers warmed up, they could view and purchase pictures of their group on the platform and jumping in on computers in the warming tent, similar to snapshots taken during rollercoasters at amusement parks.

In 2006, nine Polar Plunges were held across the state, where more than 6,000 participants and 20,000 spectators raised more than $985,000.