KEY LARGO (CBS4) – Love was in the air, or should we say under the sea, off the coast of Key Largo as boulder corals in the Florida Keys National Marine Sanctuary released millions of gametes in a once-a-year synchronized mass-spawning ritual.

Night divers in the Florida Keys had an opportunity to witness the annual "sex on the reef" session.

Some divers traditionally describe the spectacle as an underwater, upside-down snowfall.

The spectacular white excretion enables the eggs and sperm to enter the water in massive quantities, maximizing the chances of fertilization and overwhelming predators with more food than they can consume.

When egg and sperm unite, the resulting larval-stage "planula" ascends to the surface to drift in the current and grow. Eventually, within days or months, the planula settles to the bottom to grow into a polyp. The polyp then develops into a coral head by asexual budding, creating new polyps.

What triggers this fragile phenomenon remains unclear, though scientific observations indicate a strong connection between the coral spawn and seasonal lunar cycles as well as water temperatures, tidal and 24-hour light cycles. The spawning normally occurs several days after August and September full moons.

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