I can't speak for where it's going to land this list (I'd say B-tier is good), but one thing it has over most Water-types, outside of the high join level, is that you can just give it four HMs (Water HMs and Strength) without impacting its perfomance significantly (the only loss here is you cannot run Thunder and Blizzard on it, but Gyarados has a fairly low Special Attack, so I doubt it'd make good use of those anyways). With that said, it doesn't destroy the whole game, but from memory, it's never a deadweight anywhere, which is why B-tier seems good to me (I'd have to check logs for more information)Can someone explain why Gyarados is (or at least was in the previous thread) ranked higher than Quagsire, Slowbro, Tentacruel, and Lapras? Despite having high physical attack, Gyarados usually does less damage with return than all 4 of these other Pokemon do with their STAB attacks. I get that the level 30 appearance makes Gyarados great against the next 3 gyms, but how does it remain useful in the late game?
Quagsire has somewhat underwhelming stats despite the decent typing and falls off more heavily later on in the game, from memories. Wooper is also rather eh before evolving into Quagsire, though at least it's usable on the field to make this a non-issue. This is me speaking from memory, though, I'd have to check my logs to see how it performed, but C-tier sounds just right for it (I wouldn't say it's better than the Nidos, which are pmuch agreed to be C-tier iirc)
Slowbro is very slow and thus easy to wear down, especially with the amount of hax that is present in the games. You also have to backtrack for it, as using Slowpoke is pure insanity and you are better off just catching it as Slowbro (esp because Slowpoke evolves very late and thus you get Slowbro earlier with the backtrack). I think I had suggested D-tier, though I may have also suggested C-tier as a generosity. Slowking, while I haven't used it, will most likely perform similarly, as the only difference from a quick look is reversed defenses
Tentacruel, idr how well it performed, but I'd guess it's similar to Gyarados in that they are mid-game Water-types in the Slow growth rate, C/B was what I had in mind when I used it, leaning more towards C. Unfortunately, it doesn't learn Waterfall, so you cannot stick all HMs on it and call it a day
Lapras, arguably, could be B-tier as well because of natural Ice Beam, making it particularly good against Clair (you outspeed all Dragonair iirc, so you can just OHKO them), though I think the Lance matchup was worse than expected (mainly cause Dragonite outspeed you). You do need to backtrack for it and deal with a Slow growth, but I think B-tier is more than enough