PORTLAND, Maine » The Lobster Dip was launched 21 years ago as Maine's first happening where people could raise money for a good cause by stripping down in the freezing winter air and running half-naked into the bone-chilling ocean.

These days, it seems as if everybody's taking the plunge, and that is threatening to saturate the fundraising field.

Cold-water charity events have even spread as far as Hawaii, where volunteers plunged last fall into a pool filled with iced-down water to raise money for Special Olympics Hawaii.

Rocky Frenzilli helped organize the original Lobster Dip to benefit Special Olympics Maine and has seen it grow from about 15 participants to more than 300 each New Year's Day at Old Orchard Beach. Since that first Dip, he has greeted each new year with an icy splash.

Some people call him crazy, but he says it is his way of giving back to the community.

“;As long as I'm physically able to jump in the water, I'll continue doing it,”; said Frenzilli, 60, a high school teacher. “;It makes you feel real warm inside when you're doing something special for other people.”;

However, the growing number of such events and the limited number of people crazy enough to jump unprotected into icy water is raising questions about whether these polar plunges are losing their luster and cutting into one another's fundraising efforts.

These fundraisers in Maine benefit a host of groups, including Special Olympics and Camp Sunshine, a lakeside camp for children with life-threatening illnesses and their families.

They are all great causes, said Phil Geelhoed, president and CEO of Special Olympics Maine. But he is concerned that they might be taking away from the Lobster Dip, which raises about $40,000 for Special Olympics. The figure has been flat in recent years.

“;My concern is we haven't been able to grow our event beyond the point that it's gotten to, maybe because of the competition of other plunges around the state,”; Geelhoed said.

Special Olympics chapters now hold more than 40 Polar Plunges each year, raising more than $10 million. One of those dips drew more than 3,500 people who dived into the Atlantic Ocean last February at Virginia Beach, Va., raising more than $850,000.

One of the newcomers, Maine's Camp Sunshine, held its first Polar Dip in 2006; this winter, it is holding 10 of them in eight Eastern states, from Maine to Virginia, and even one on the Pacific coast in Seattle.

They are so successful—they raised $150,000 last winter—that the camp is thinking about taking a page from Hawaii's playbook and holding one in Florida in an ice-filled swimming pool, said Michael Smith, Camp Sunshine's director of special events.

The idea of greeting the new year with an icy blast of water is not necessarily new. Hardy groups have been doing it for years, especially polar bear clubs in northern Europe. It's the idea of cashing in that is relatively new.

When a certain type of fundraiser is successful, it's only natural that others will imitate it, but such events typically have a life cycle of waxing and waning, said Michael Nilsen, spokesman for the Association of Fundraising Professionals in Arlington, Va.

For example, the 1990s saw an explosion of fundraiser walk-athons, bicycle rides and running events.

“;When organizations see something that works in their community, they might try to copy it,”; Nilsen said. “;At some point they might reach the oversaturation stage.”;