A unique sub-sea concert had about 400 divers and snorkelers rocking this past weekend as they explored part of the continental United States’ only living coral barrier reef.

The Lower Keys Underwater Music Festival took place Saturday at Looe (pronounced “Lou”) Key Reef, located about 6 miles south of Big Pine Key in the Florida Keys National Marine Sanctuary.

The quirky sea-focused songfest spotlighted coral reef protection and eco-conscious diving in the Keys’ colorful ocean environment.

The four-hour musical event was staged by local radio station US1 104.1 FM. Participants swam among Looe Key’s marine life and coral formations while listening to water-themed music broadcast by the station.

“Interspersed with the music, we have public service announcements — kind of diver etiquette, coral reef awareness messages, so people have less of an impact on the coral reef,” said festival co-founder Bill Becker.

The music was piped underwater through special Lubell Labs speakers suspended beneath boats above the reef. The oceanic playlist included melodies like the Beatles’ “Yellow Submarine” and the themes from “The Little Mermaid” and “Gilligan’s Island.”

According to Becker, even the fish seemed to sway to the music.

“I’ve seen a big school of yellowtail right below the boat here and they were gathered right around the speaker,” he said. “I imagine it’s something unique for them. They don’t normally hear music underwater — I hope they appreciate it.”

The primary purpose of the annual festival is to encourage preservation of the Keys’ rich coral reef ecosystem.

Some divers wore costumes, portraying everything from mermaids to marine iguanas, and pretended to play underwater musical instruments sculpted by Florida Keys artist August Powers.

“You know, this event is so special because it pays attention to the coral reefs and gives a lot of respect to it,” said diver Nichole Blackburn, who came from Redondo Beach, California, to participate in the festival. “It really celebrates our ocean and what we’re trying to do to preserve it.”