Take a second camera body like 7d mark 2. Perfect with 100 - 400. You will find your 16 - 35 on your full frame very useful for the beautiful landscapes.
B & H may actually provide a selection of lens to try.
I found a dry bag, polarizing filter and waterproof pocket camera TG5 very useful.
You will really enjoy the scenery!
You may wish to try extensions tubes with your 135 mm lens. This will make it a nice macro lens for flowers. Then you may another lens for landscapes...perhaps a 50 prime 1.4....This lens will also work very well with extension tubes for macro. This would be an inexpensive way to start out and still provide excellent results.
Avoid rapid changes in temperature when you come in from going ashore....I just left my camera in an overboard dry bag until everything came to about room temperature. I also found the Ruggard Parka cold and rain protector very helpful when out in the cold weather while on land excursion and while taking photos from the bow of the ship.