HAWAI‘I • Big Island
Field Entry 03
March 2024
Tour Operator: Jack’s Diving Locker
Manta Rays & Filter Feeding Under Night Skies
I drove to the marina just before sunset. Three kids with me — ages 11, 9, and 7 — excited and slightly nervous.
We loaded onto the boat and motored south along the Kona Coast for nearly an hour, watching daylight slip behind us. After sunset, the ocean quickly turned dark.
When we arrived at our snorkel destination, we weren’t far off the coast, a few hundred feet maybe. The distant shoreline was visible against the dark horizon — close enough to see, but not close enough to feel comforting. It offered little sense of proximity or familiarity. Beyond that faint outline, there were no landmarks — just swells and stars.
We suited up in wetsuits and slipped into the dark Pacific waters. Our boat wasn't allowed to motor directly into the feeding area, so we entered the water and swam roughly 30 feet toward the floating light board the tour operators had positioned nearby. There was no visible bottom — just open ocean and the surface rolling gently as we reached the board and held on. The floating board fitted with powerful lights that shone downward into the water column below.
The lights were not for us.
They were designed to attract plankton — microscopic organisms drawn toward illumination. In the darkness, light becomes a gathering point. Zooplankton concentrate in the beams, forming a dense vertical column of suspended food.
The manta rays were not interested in us. They were feeding in the plankton concentrated in the light.
Filter Feeding & Ocean Productivity
Manta rays are filter feeders, like baleen whales and whale sharks. Instead of teeth built for tearing, they have specialized gill rakers that strain plankton from the water as they swim.
At night, many plankton species rise toward the surface in a phenomenon known as diel vertical migration. This nightly movement concentrates microscopic life near the surface — and artificial light intensifies that concentration even further.
The illuminated water beneath us created an intensified feeding zone.
When the mantas rolled and looped through the beams of light, they were not performing. They were following energy. And yet to us, it was the most incredible performance.
Their wide mouths opened as they glided forward. Cephalic lobes unfurled to funnel plankton-rich water inward. Each barrel roll allowed them to remain within the densest patch of food, and some of those barrel rolls ended inches from our masks.
Observing in the Dark
I never held the board.
Not once.
Instead, I held one hand on each of the two younger children beside me, constantly tracking their bodies and faces. My 11-year-old floated across from me, steady and wide-eyed.
The swells rose and fell around us.
It was nerve-wracking and awe-inspiring at the same time.
I experienced the manta rays by watching my children experience them — their masks tilted downward, their bodies going still each time a massive wing swept beneath them, and the muffled squeals that came from their snorkels.
When we climbed back onto the boat, it took a few minutes for everyone to process what we had just seen.
And in that dark Pacific water, holding tight to small wetsuits while massive wings circled below, I was reminded that observation is sometimes as powerful as participation.
Kristen
Creatures Are Our Teachers™
Let Science Run Wild.
