All around me, people in wetsuits are seriously losing their cool.
Squeals pierce the darkness as we float, looking into the ocean just off Hawaii Island's Kona coast.
The weird thing is I'm one of the screamers.
Some of us are squealing through our snorkels - unable to look away from the manta rays somersaulting within centimetres of us as they catch dinner.
Others having similarly close encounters with these gentle giants are coming up for air and gasping from astonishment.
These manta rays are so big - think several metres from wing tip to wing tip - that they could easily enfold us within their wings and make us disappear.
Not that they would - manta rays also have electro-receptors allowing them to steer clear of objects in the water.
We've all just flopped off the 55-foot Hula Kai catamaran.
It departs from a dock that's a five-minute walk from the Sheraton Kona Resort and Spa, which plays a crucial role in this adventure.
In 1972 the newly built hotel, then called the Kona Surf Hotel, kicked off the whole manta ray thing by shining spotlights onto the waters below its black-lava cliffs.
Little did the hotel know the lights would attract plankton, the manta ray's favourite snack.
Spotlights still shine out onto the water today - diners at the hotel's Rays on the Bay can easily spot manta rays from the restaurant balcony and later, from my oceanfront room, I watch swimmers frolicking with the rays late into the night.
Like any encounter with wild creatures, there's no guarantee any of the Kona coast's 150-plus manta rays will turn up at the Manta Village, as this spot is known, on any given night but 2012 statistics show they appeared 93 per cent of the time.
We wonder at first if we're among the unlucky few who don't spot a thing.
After clambering into our wetsuits on shore and into our flippers as we climb off the boat, we line up along a long, foam-filled raft fitted with plankton-attracting spotlights.
Each of us wriggles a foam noodle under our ankles to stay horizontal so we don't accidentally kick the main attraction.
We've already had a talk and a question-and-answer session on the deck: we're reassured that manta rays don't have barbs like stingrays and can't bite us as a shark might.
We'll be perfectly safe out there. The boat captain, Mitch, says the wetsuits will keep us warm.
That notion is challenged once we're in the ocean for a while.
Five minutes in, two rays glide by and quickly disappear.
I'm struck by how much their upper skin looks like black velvet, how big their wide-open mouths are, and their sheer size.
Then we wait. And wait.
Twenty minutes in, with cold creeping into our bones, the woman opposite me on the raft makes her way back to the boat.
As I obsess about how a cup of hot Kona coffee would warm me up, there's squealing from the next pod of snorkellers (by no means are we the only group out here - there are other snorkellers, swimmers, kayakers and paddle-boarders).
We spot the cause of the commotion.
A manta ray has not only appeared - it's doing somersaults, flipping up and over, up and over, revealing its pale underside with distinctive spots that help establish if we're looking at Vallaray, Jana Ray or Reece Ray (the manta rays' markings and names are documented at mantarayshawaii.com).
The ray almost brushes the swimmers as it nears the surface - and that's what the screams and squeals are about.
Even though I know the trio won't touch us, it's hard staying calm as a manta ray rises almost to my face with mouth agape, feeding on the snowstorm of plankton.
Water is leaking into my mask, my snorkel is waterlogged, too, but I almost forget to breathe as the expanse glides right past with centimetres to spare.
It's one of the most unforgettable marine encounters I've had.
I've no idea how much time passes as I watch this unfolding underwater ballet. At some point the rays move on and I look up to realise I'm among the last in the water.
A change of clothes warms me up once I'm back on board; vegetable soup and cups of hot chocolate help, too. I'll do a lot of other things in Hawaii but nothing, it turns out, will beat this.
The writer travelled courtesy of Holiday Specialists, Hawaiian Airlines and Hawaii Tourism Oceania.
GETTING THERE See hawaiianairlines.com.au. Apply for US travel authorisation before departure. See https://esta.cbp.dhs.gov.
STAYING THERE Rooms at the Sheraton Kona Resort and Spa at Keauhou Bay cost from A$125 ($144) a person a night, twin share, through Holiday Specialists.
SEE + DO Snorkellers must be at least seven years old; tours start nightly from sunset at Keauhou Bay, Kailua-Kona, Hawaii Island, USD$99 ($126.5) a person. See fair-wind.com.
- Sydney Morning Herald