We had 4000 meters of deep blue water beneath us today and flat, calm winds with a lazy, languorous swell from the north. As we closed in on our next destination, the Cape Verde Archipelago, we had seen more birds in the air – yet more boobies, frigatebirds, and storm petrels. The surface of the water was at times literally alive with flying fish, skimming for yards ahead of the ship.

We took to the water ourselves after lunch. Out in the middle of the open ocean, with nothing on the horizon but the haze of low clouds blurring the boundary between ocean and sky. All one haze of cerulean blue, darkening to ultramarine clarity around National Geographic Endurance.

Jumping from Zodiacs into the wild blue yonder, we thrilled at the prospect of such depth beneath our bodies – ethereal in its majesty. At one with the ocean. Timeless.