Nearly 500 divers and snorkellers submerged in the Florida Keys National Marine Sanctuary for a "concert" beneath the sea broadcast by a local radio station.

The 30th annual Lower Keys Underwater Music Festival, held at Looe Key Reef along the continental United States's only living coral barrier reef, featured four hours of ad-free music piped below the surface via a series of underwater speakers. "We started this as an arts and cultural event 30 years ago (and) thought it would be a one-time thing," said event co-founder Bill Becker. "It's the only place we know of where music is put underwater for divers, snorkellers and the marine life."

The water-themed playlist included such tunes as the Beatles' Octopus's Garden and the themes from Disney's The Little Mermaid and television classic Flipper about a dolphin at a marine preserve in southern Florida. Participants described the music as clear and ethereal, with underwater visibility of about 15 metres.