I'd like the point out that Ike is actually awful at water camping. He can't really do anything once his opponents who are actually fast get alongside him in the water. If you want to test how powerful it really is, Mr. Game & Watch, Meta Knight, and Jigglypuff are the actual best characters at it.
With Mr. Game & Watch, his up special is actually hard to beat out (unlike Ike's), and he is fast and good in the air otherwise (also unlike Ike). When the rock comes, he can just glitch inside of it, removing one of the primary "disruptions" from his strategy (though even Ike can just get in the water to the left of the rock and make an Aether wall there). If you think the ship going in the air is actually going to stop him, you're nuts. I wait to jump out until the last minute and get on the ledge, using my full ledge invincibility. I probably touch down on the stage once and avoid you as best I can. Then I jump out over the stage in the low gravity and up special pretty high and let my parachute carry me down safely for a while either to the ledge if I went too early or more likely back into the water. I CAN stay in the water essentially forever. If you can't come out and beat me in the water, you lose. I am 100% willing to wait to win by time if I'm up.
I'm going to be looking for more games on this stage in the future, but it seems pretty obvious that this is degenerate in a way planking isn't even close to being (planking being something that obviously should not be banned). You aren't even particularly close to the stage when water stalling which gives the guy in the water a ton of time to react to what you are doing, and you have tons less enforced lag. No characters can combo you across a ledge into an instant kill ship bow or off a "swim off" either. On a ledge, you are at extreme risk if they do manage to hit you; in the water, you're not really at much risk at all unless they are from a pretty narrow subset of characters.
Appealing to the status quo (it receiving mostly votes to allow it) doesn't really prove anything; it's actually just plain baffling that Pirate Ship gets the support it does, especially more than stages that seem pretty obviously better than it (Distant Planet, Norfair, Green Greens, Yoshi's Island [Melee], Port Town Aero Dive, Corneria, Onett). This isn't even a "ban everything" rant or anything close; I want almost every even plausibly legal stage legal, but even still Pirate Ship seems obviously awful.
Also, with water stalling, comparing the tactic in any way whatsoever to what you can do on Delfino Plaza, a stage that has water for incredibly brief amounts of time, is kinda silly. It's like equating the walk-off on the Halberd with the ones on the Bridge of Eldin; they are really that close in terms of how much they matter. The tactic is really only worth talking about in the context of Pirate Ship, and I do confess that beyond being overwhelmingly obvious to me based on my experiences I don't have any direct evidence, but at the same time I don't see any evidence that people seriously try to abuse it in a competent way.
I suppose I should end with this question. If you are using Mr. Game & Watch, Meta Knight, Jigglypuff, Toon Link, or Ness, what is your motivation, if you have a lead on Pirate Ship and are not matched up against an opponent who is especially good at countering water stalling, to do anything but hang out in the water? What advantages does being on the stage provide you over being in the water? I see no real loss to being in the water; removing ground moves from the game entirely seems pretty cool for those characters.