Just finished a trip in Svalbard by ship, including up to the pack ice (82" 34' North !), I'd expect similar conditions as Antarctica.
Monopod - I brought one, and used it a little, but basically it was useless on the boat due to being cumbersome, and hard to maneuver quickly during 'action'.
I also tried it once on a Zodiac but you can't keep up with the boat movement sufficiently.
Tripod - Used on deck with 800mm lens a few times, worked fine, However it was generally when ship engines were off and we were sitting in the ice, or drifting.
Mainly used on-shore for wildlife.
Both are useless when boat is moving / rolling or doing anything annoying. And forget it on a Zodiac.
Hand holding and higher ISO is the best way to go. Just Sling the lens when not in use, and get good at bringing it up fast to shoot at the right zoom.
I shot most of the trip at ISO 1600 and sometimes 3200, no problems. (Canon 1dX).
For ship or Zodiac Carry I recommend a Rapid strap. (especially the Double carry strap).
I am unfit, but fairly tall (6'3") and found slinging a 1dx with 200-400, and 1dx with 70-200 or 24-105 on a double strap worked extremely well both on the ship, and on Zodiac cruises.
You can wear them easily under a lifejacket, just need to remember to put it on first, and make the straps longer.
Tripods really only got used ashore.
Bean-Bags on ships rail worked well for 800mm Lens, although due to constantly changing target position, generally ended up hand-holding that also.
Many people with long lenses started by trying tripod onboard, and most ended up hand-holding for the rest of the trip.
Regards
Mark.