Wishiwashi is definitely a neat concept for a pokemon, and an interesting take on similar concepts like Archeops or Regigigas with the ability not really crippling it that much, but it suffers more from a poor movepool and that low hp. It's essentially slightly tankier than a non eviolite Dusclops. Which is to say, it is quite tanky, but it won't be sponging hits for days or anything. The typings are comparable too, with ghost only having two weaknesses as well though less resistances. Of course, this fish is a lot more offensive than Dusclops which is why it's more of a wallbreaker than a tank. But still, having some kind of reverse Zygarde Complete effect where it started off with more HP (like 70-80) just to be really bulky.
Or just having recovery would solve the issue as well. Then you could recover on a predicted hit that would drop you below 25 percent, go back to your schooling form and go from there. (I assume, anyway, that it works like Defeatist) Without anything beyond rest, though, you're prone to being worn down quick.
More coverage is desperately required as well. No boosting moves either, which is a shame. Ice/Ground/Water is decent coverage if not a bit redundant, but still, when that's literally your only option, it's lacking to say the least. If it had a better moveset, it could reasonably work as just a mixed wallbreaker that could threaten physical and special types alike with its excellent offensive stats. It can still do that, to an extent, but it still ultimately disappointing that it has no utility, no recovery, little to no coverage, and little flexibility. It's just a really hard hitting Water type, which is neat ,but there's not much else to it.
