We had a whole unit on pelagic communities, the bodies of fish that live in the open ocean and not near the shore or the sea floor. I found their migratory patterns spellbinding. Some tuna complete migratory journeys that are 5,000 miles long, and they do it when they’re only one year old. For a moment, I let myself wonder what my life would be like if I had decided to follow in Millie’s footsteps. Instead of tweaking slide decks in a cubicle, I could be thinking about marine life. Maybe, I think, maybe I would have met Hugh on my own, not through the lens of Millie’s disdain, or through a veil of pretending to be her. Maybe I would have gotten myself published in The Marinist.

Vanessa’s roving flashlight interrupts my thoughts. Andrew has gained his buoyancy. It’s time to move.

We follow Vanessa blindly, kicking towards her flashlight, dutifully pointing our army of beams at the ground. One of the hardest things about diving at night is that it’s shockingly easy to blind your fellow divers. A flashlight to the face compromises your vision instantly. But, because you can’t see hand signals, flashlights are the only way to communicate. You have to use your flashlight to signal to others, to ask how much air they have in their tank, and to tell them you’re OK. You’re supposed to point your flashlight at your own hand to make it visible, but sometimes the ocean’s currents move the flashlight and point the beam in a different direction. It’s a tricky business.

Miguel turns on a special flashlight that lights up the bioluminescence of the reef. I am struck to find that once again, a fact resurfaces from the depths of my brain. Corals absorb harmful rays from the sun and turn them back into pink, purple and green bioluminescence. All of us are still as we watch the reef light up under Miguel’s blacklight. It’s as if we’re at an underwater rave – every coral is lighting up a different colour. There’s blue, and green, purple, yellow, pink. Like someone passed out different coloured glowsticks.

We start moving again, slowly. My gaze strays from Vanessa’s beam and into the black abyss beyond. Past the light of my flashlight, I imagine an army of sharks, sitting and waiting for me to get separated from the group. Sometimes I cast the beam of my flashlight out into the distance to make sure nothing is lurking there, but I have yet to see anything in the pitch-black open ocean.

I see Vanessa’s flashlight moving in a fast circle, which means ‘PAY ATTENTION’. Then, she pivots the beam into the dark, dark blue. A pair of pale eyes reflects back – a shark.