Ernie is perfectly right that a tripod is great for locations where this is permitted - on larger vessels, but you need to check what kind of vessels you will be doing your watching from. As I said above, for H&S reasons and to stop annoying your fellow clients, on smaller boats and RIBs they are generally prohibited. You might be advised to consider a monopod and see if it is permitted. Also a monopod, while supporting your camera lets you pivot in many axes almost instantaneously. Personally, I found hand-held worked best as the whales can move so fast, that any support can become an encumbrance, and can catch on seats or (worse still) foul other passengers. Frankly, you will spend a lot of the time with your camera on your lap while the boat looks for, and manoeuvres around pods of whales. Also, if you are on a small boat (not RIB), one needs to share the space with other photographers so one moves around a lot on deck and other encumbrances, such as tripods and monopods can waste time and get you in a tangle. Again, I strongly suggest checking with the tour operators as to their protocols.
If you do want a compact and efficient camera support, there is one unit that I got recently that is actually a sort of combo of both tripod and monopod, without the disadvantages of the widely splayed legs of a conventional tripod. It's the iFootage Cobra 2. You can see from the image below that it gives you three support configurations: a tripod, monopod and mini tripod. The units clip and switch options very quickly and there is a special ball-head connection at the foot in tripod mode, so you can adjust the tension on the tripod for fast or slow movement as it pivots. They are actually designed for video work, but that makes them very suitable for wildlife photography.
You have to get your own head to connect the hole in the base of your camera to the top of the unit - I got a SmallRig Aluminum Panoramic Ball Head 3034 for mine and it works fine.
