If the goal is wildlife, he's going to want as much reach as possible. I had a 28-270, non I/S, that was f6.3 at the long end and it wasn't enough to catch good photos of whales and distant birds. I needed a faster lens with I/S. The 70-200F2.8 with a 1.4x or maybe a 2x would be a good start. Is your 70-200 an I/S lens? That would also help a lot.

A very long lens would give added reach, but then he will need a tripod, but that would be a huge challenge to use on a crowded, rocking ship.

You can get get good scenery photos with regular focal lengths, though. I used my 28-135 and my 12-24 for these.

I had one, although the shutter stopped working. I had 3 lenses that I sold for $80, but the gentleman ddidn't want the camera. I sadly had to throw it away.