It was on a trip to the Cayman Islands, Little Cayman to be specific, that I acquired my conflicted sense of wonder and discomfort in the sea.

I was a teenager, snorkling the surface waters of Bloody Bay while family descended the vertical cliff known as the Great Wall West.

Below me to one side, a bright sandy seabed, perhaps 20 feet below. Sunlit, crystal clear. To the other side, darkness as the sea floor dropped away in a steep underwater wall.

As I floated on the sunny sea, a fever of several large manta rays approached below. Gliding smoothly along the sandy floor, they appeared in my range of vision, and then swiftly floated out over the lip of the great wall and swooped into blackness.

It wasn’t the size of the rays, the number of them, or the distance between me and them, that sent shivers down my spine.

It was the thought that if such strange animals could vanish so quickly into those dark depths, then almost anything could come right back out with no warning. They were in their element; I was out of mine.

Last year, images emerged of a previously unknown species of snailfish found five miles (8 km) deep into the Pacific’s seven-mile-deep (11 km) Mariana Trench. The deepest known fish ever recorded.

Fragile in appearance, ghostlike, the 6-inch (15 cm) fish was on the hunt for prey when caught on film by an international research team using the Hadal-Lander, a deep sea exploration vehicle.

But how fragile could the snailfish be, really, if it is able to survive and hunt five miles down?

For the first time, researchers also filmed and collected a ‘supergiant’ amphipod over a foot long (34 cm), a massive version of creatures normally sized between 1-1.5 inches (2-3 cm).

The teams and technology behind the Hadal-Lander exploration work to understand what we know about the environment, animals and the various geological and ecological processes of the deepest ocean region on the planet.

Meanwhile, over at the Sea Life Aquarium in New Zealand, Sony managed to teach an octopus how to use a water-resistant camera to film visitors on the other side of the aquarium glass. The octopus, a female named Rambo, took only three tries to get it right, faster than most humans. Even if it’s only for a marketing stunt, that’s one smart beastie.

I marvel at the breadth and array of aquatic life, at types of intelligence so different from our own; I respect the phenomenal physical capacities to withstand extreme water pressure and thrive in darkness. It is truly a different element.

And it’s just as I suspected way back on the precipice of the Great Wall West all those years ago: Our oceans are full of creatures with all manner of tricks up their fins, tentacles and tails.