Kailua-Kona, Hawaii – It’s night on the ocean, but I’m floating in a sea of light. Above there are stars, and below nine manta rays ranging from 7 to 16 feet across are busy feeding on microscopic plankton. The plankton are drawn to the lights of two dozen divers stationed on the sandy seabed 40 feet below me.
I’m snorkelling on the water’s surface with a dozen others, our flashlights aimed downward, adding to the light show. The mantas seem to dance between the beams of light, their grace belying their massive size.
I’m a spectator at a ghostly underwater ballet in which the half-tonne creatures turn lazy somersaults. The first half of the loop is done feeding face-down; then a graceful flip exposes the ray’s white underbelly.
Each belly has distinctive markings that, like fingerprints, identify the rays to local enthusiasts. Tonight I encounter Big Bertha, a female ray who at 16 feet is the largest known manta in the region.
Bertha was first identified by divers in 1992 and is a frequent visitor to Ho’ona Bay/Garden Eels, my dive spot for this night. Although mantas are found in tropical and temperate waters worldwide, this night dive is unique to the Big Island of Hawaii.
In the 1970s, local hotels such as the Kona Surf shone bright lights into the ocean to add nighttime romance. The light drew in the plankton, who then drew in the rays, who then drew the divers, who then brought more light – it’s a circle of life story.
The 100-plus mantas who frequent the Kona coast of the Big Island have learned that divers are the best maître d’s. The mantas will swim right at you or, more accurately, your flashlight. They get so close that you can see straight into their cavernous mouths.
It’s a surreal sight. Since mantas have no visible teeth, we get a clear view through to their gills. They’re close enough to pat, but doing so will get you exiled to the boat, since a touch can rub away the ray’s protective mucous coat.
Mantas have no defence mechanisms, no barbs or stingers, unlike their infamous cousins the stingrays. Despite their size, they’re harmless to people; their “devil ray” nickname stems from their horned appearance, not their behaviour.
Mantas weigh 100 pounds for each foot of span, and to stay healthy they must eat 10 per cent of their body weight daily. For a medium-sized manta of 1,000 pounds, that’s 100 pounds of chow each and every day.
Since their food is plankton, some of the smallest creatures in the ocean, it takes quite a bit of eating to reach that mass. Fortunately, dinner for a manta is mostly a matter of swimming around with its mouth open.
A manta will uncurl its distinctive “horns” on either side of its head and use them to funnel water into its gaping mouth. Inside, filters trap the plankton while the water flows back out through its gills.
It’s a simple process that’s mesmerizing to watch. That’s why this experience has consistently shown up in diver magazine top-10s over the past two decades.
The show goes on for well over an hour. As a snorkeller, I can stay in the water until the last of the divers, reluctantly driven to the surface when their tanks run out of oxygen, return.
Once we’re all out of the water, the rays continue circling the boat, grabbing their last snacks before we head back to shore.