LV Moose wrote in post #17614248
I've been on two Alaskan cruises, and while I got a few shots of breaching whales at a distance, some Albatross, and a couple of eagles on shore and flying past the front of the ship, I don't think I'd bother with the 500. None of those shots were really "keepers" for me; it was more of a pastime. The good shots came from excursions, and your 100-400 Mk II should be perfect for that, and "good enough" for taking shots from the ship, especially with the 1.4X TC added.
I have been on two Alaskan cruises, too, including last summer, and I concur with Moose. While on board, there was very little to shoot with a telephoto lens. On last year's cruise, I think I used one only for a few close ups of the glaciers in Glacier Bay National Park. I used my 100-400L extensively on two whale watching excursions, though. As a veteran of 10 whale watching trips in Alaska, Hawaii, Maine and Boston, I think a long prime would be too limiting for this activity, as the whales can get quite close to the boats (especially if it's a small boat) and you need to react fast. Also, you will want a more nimble lens, as you will be moving around the boat a lot trying to position yourself for the next whale surfacing. Hence, a quality zoom telephoto is ideal for this type of excursion. For other whale watching trips, I found that my 70-200 f/4 IS on a crop body was enough reach. In fact, for our next Hawaii trip I doubt that I will bring along the 100-400L II, and will just bring that smaller, lighter telephoto.
If you plan on a whale watching excursion, I would recommend bringing a monopod. I used one for the first time while whale watching last summer, and it was very useful. You need to be in position ready to shoot, as you will only have a couple of seconds when the whales surface. The monopod made it easier to keep the 100-400L in a ready shooting position without my arms getting tired. A tripod is too big and cumbersome to move around with and setup on a small boat.