My favorite cruise line is, of course, SIO. The fare is quite reasonable, $0, and the chow is good. However you eat cafeteria style, on bare Formica tables, while on my second favorite, WHOI, one has a white tablecloth and is served by mess stewards.
One has to make do without the rock climbing wall, but one is allowed to climb the mast to untangle balloon tethers, etc.
Ports of call include Papeete, Tahiti, Bounty Bay on Pitcairn Island, and Antofagasta, Chile where I spent a rousing New Years Eve watching the Bosun go to sleep while waiting for the otherwise deserted bar to fill with revelers—which happened around 11 PM.
Shipboard recreational activities include tossing 64 pound cases of TNT over the side, piston coring, and hauling in the streaming hydrophones and magnetometer while still doing 14 knots.
A common misconception is that R/V means Research Vessel, but we know it really means Recreational Vehicle.
Marty