PACIFIC BEACH -- An estimated 5,000 revelers joined the "Floatopia" floating party Saturday in Mission Bay off Pacific Beach, where, according to initial reports, authorities arrested a dozen mostly young people for public drunkeness, rescued two from the water and gave medical aid to another half-dozen.

On Monday, Garry Hassen of the San Diego Police Department said police issued 30 citations and took 20 people to detox. Of the 20 taken to "dry out" in detox for four hours, two were rejected and taken to jail instead.

The crowds of rafters off Fanuel Street Park had been swelling since about 9 a.m. as partyers on Spring Break take advantage of a city loophole in a ban on drinking on the beach. The ban does not extend into the bay or ocean.

"A lot of people are intoxicated here," said police Capt. Christopher Ball, who spent most of the day monitoring the loosely-organized event. "Some people are leaving now and some are still coming in.

"Traffic wasn't bad because these people walked four, five, six, eight blocks to the beach. There's a high likelihood we'll have some drunk driving."

Ball said there were no fights or serious injuries, but two people went to the hospital because of severe intoxication. Those arrested were taken to detox, not jail, he said. San Diego lifeguards rendered medical aid to six or seven drunk people, a lifeguard dispatcher said.

The gathering was promoted on a Facebook page, where more than 10,000 people lodged an RSVP that they would attend. Similar off-shore gatherings took place last year with crowds in the thousands, The San Diego Union-Tribune reported.

Ball said the crowds appear to be mostly college-age locals and visitors on Spring Break. Many were under-age for drinking.

"They come without alcohol, but they get out there on a float and there is alcohol out there," Ball said. "When we get them, they're drunk."

He said some people got onto the water by 9 to 10 a.m. and started drinking then. A strong force of police and lifeguards were on hand all day.

San Diego voters approved a ban on drinking on city beaches in 2008.