Water has a couple of perks, one is you'll get an amphibious form to use on land.
Second, there are enough mobs that use water attacks that you're immune to to rank on early once you get your first form that you can power rank.
Third, with water major, you get the gills greater enliven which allows you to use any other form underwater, so you don't need to take water as a minor focus.
Fourth, the other enlivens are all pretty good, hide of the walrus for DR, brutlaity for dam, litheness for dodge, so you're going to have something for pretty much any other form to use.

I ended up with great white and komodo, which is flat out insane for ranking.
I also had the hippo as my 3rd tier, which with stoneskine and hide of the walrus could tank sahuagins in the ruins of the deep with relative ease, though I would have to heal between fights.
But at 2k+ xp per, you can see how they rank so fast. If you can find anyone to heal you, you can probably hero in maybe 20 hours from whenever you get that form (if you get it)

At later ranks, I would just put up gills, go great white and hit mobs for annihilates, when you get hurt go into komodo and recover insanely quick.
Plus, komodo can plague things, and has decent damage output with it's normal attacks and rake.
But that combo has 0 lag, so in PVP it is almost worse than useless, unless you catch a rager and spam swinto (if you have the damredux to take the beating you're going to get, since shark tanks for shit)