We dutifully follow her, our fearless leader, towards the reef. The sweetlips fish disappear in our wake. We swim over another giant clam, ringed in neon purple barnacles. Colourful fish are hovering above it. One of them is purple. There is a yellow stripe down its back. Before I can see if it has an extra fin on its underbelly, it twitches its tail and swims away. I want to believe it was a butterfly wrasse, but I can’t be sure.

The further we swim the more my anxiety rises. My breathing is picking up. I check my PSI. I’m taking in more oxygen than usual, unable to regulate my intake with my nerves spiking. Hugh notices, reaching for my hand, letting his fingertips brush mine.

I take out my digital camera and hold it in one hand, trying to manifest a butterfly wrasse appearing. Hugh notices and our eyes meet. He flashes me a thumbs-up. I try to ignore the fact that if I find these fish, he’ll lose his promotion and his publication opportunity.

We follow Vanessa towards a looming coral structure. It’s the most colourful one we’ve passed so far. The ocean floor is dotted with blues, pinks, purples and yellows. There are huge cracks and crevices with fish teeming in and out of them. I see the telltale flash of brown spots — a pufferfish darting between the rocks. I struggle to remain optimistic and enjoy the dive – it’s one of the best we’ve been on, but I don’t feel that familiar tug of excitement as the group passes over a brain coral with a large crab scuttling over the top.

Someone in the group spots a moray eel. I see a flash of its large dark-green mouth and I back up, away from the hole it’s hiding in. Moray eels are dangerous. Their jaws are extremely strong. But their long sleek forest-green bodies are also hypnotically beautiful. Derek hovers to take a picture. We see another crab scuttle across the rock, claws waving in the air.

I station myself next to staghorn coral, camera out, and wait. I feel like every cell of my body is hoping. Familiar worries surface in my brain, that I’m not good enough, qualified enough to successfully do this for my sister. That I’m a fraud and a liar. I look over at Hugh, who is just as intently searching for the fish, and I feel guilt tug in my chest.

How will I come back empty-handed to Millie? How will I face myself, a failure, returning home to a job I hate?

I feel the commotion of the others swimming behind me. Miguel calls over the group to show them something else. I remain right where I am.