Sounder

Sounder trades ultimate depth for the view. Its pressure hull is a single cast-acrylic sphere, so a guest sitting beside the pilot sees very nearly everything the ocean has to show at 2,300 metres — the last daylight, the first bioluminescence, the wall of a seamount sliding past.

It is the most-dived craft in the fleet, and the one most people mean when they say they have been to the deep.