FLORIDA KEYS — Disposable waterproof camera, $20; scuba dive in warm clear water, $60; taking pictures while watching corals “have sex” during the dive trip, priceless.

Underwater voyeurs are to vie for spots to dive Florida Keys reefs to view the annual coral “love affair” traditionally sparked by the August and September full moons.

This rare exchange of reproductive cells fascinates divers for the sheer volume of white excretion that seemingly fills the Atlantic Ocean around the continental United States’ only living coral barrier reef, which parallels the Keys.

According to researchers, corals use multiple reproductive strategies. Nearly all large reef-building species release millions of gametes once a year in synchronized mass-spawning rituals. This “broadcast spawning” enables the immobile animals to send their eggs and sperm into the water in massive quantities.

When egg and sperm unite, the resulting larval-stage “planula” swims to the surface to drift in the current and grow. After some time — two days to two months — the planula settles to the bottom where it grows into a polyp. The polyp grows into a coral head by asexual budding that creates new polyps.

Such a copious delivery system is believed to maximize the chances of fertilization and at the same time overwhelm predators with more food than they can consume.

The exact cues triggering the annual phenomenon remain unclear, but are believed to be linked to water temperatures as well as lunar, tidal and 24-hour light cycles.

Scientists’ observations indicate a strong connection between the coral spawn and seasonal lunar cycles. Though the polyp release cannot be guaranteed to happen on the exact date, the upcoming September 2009 full moon falls on Friday, Sept. 4.

Therefore, divers should be able to participate in coral spawning night dives either Sept. 2, 3 and 4.

To learn more about seeing the 2009 coral spawn in the Florida Keys, contact any of the Keys’ professional dive operators or explore this Web site.