“Three, two, one go!” Rolling backwards off the pontoon of the RIB, I delighted in the slow-motion freefall from a negative entry, going straight down with Carlos, our Dive Master.

“At last,” I thought, “this is the life.” Yet, I had little time to contemplate the hue of the blue and the visibility, as the instant I looked down I saw a giant manta moving slowly over the cleaning station 20 metres below. It slid graciously and effortlessly through the water, butterflyfish, goldies, and wrasses nibbling it clean of the parasites it had picked up on its oceanic wanderings. We unobtrusively dropped behind a wall next to the cleaning station and watched as a second and then a third manta glided in, whilst a large green turtle settled into a hollow. What a start!

As we drifted gently along the dive site, the oddly-named Hogwarts, 100 kilos of potato grouper gave us the eye, kingfish cruised past, and a school of barracuda zipped along. My grin was so wide I nearly lost my regulator when a unique small-eyed stingray, the largest of all stingrays and only ever seen alive here, 5000 kilometres from the edge of its previously considered range, flapped its two-metre wide wings and slid past nonchalantly. It was undoubtedly the best first dive of a trip ever, and there were some big smiles on the surface, dive leader Carlos beaming even more than normal.

On the boat after the first dive, the crew changed our cylinders and we moved close to the coast and started cruising slowly, looking for the biggest fish in the ocean, the beautiful and docile whale shark. Within an hour skipper Ernesto’s eagle eye picked out the outline of one of these giant planktivores. Donning fins and masks we slid over the side and snorkelled alongside a six-metre specimen, the sun’s rays highlighting the white spotted patterns that cover its body from the tip of its tail to its super-wide terminal mouth.

Attracted by the plankton blooms ...