Hippowdown has a 112 attack stat which means he can wreck a lot of things in UU; especially with his great STAB and coverage with Stone Edge. His low speed sucks but its not like it can be revenged killed with some of the highest HP and Defense stats in the tier. His ability is just icing on the cake and pushes him past Rhyperior but thats for a different thread.
On the note of Blastoises absence, a lot of bulky water get there time in the spotlight. Let's see there's:
Poliwrath (really underestimated and loves how easy hazards are to get up and appreciates the lack of Ghosts like Jellicent, cri[ppled by Sableye but should generally be using a Sub set.)
Tentacool (Bulky with Eviolite but really harcd to maintain with no recovery outside of Rest, outclassed by Qwilfish as a whole)
Slowpoke?/ Slowking (I have never tried Slowpoke but I imagine it is decent with instant recovery and great bulk, probably outclassed by Jellicent considering all the bug types in the tier. This loosely applies to Slowking too)
Seadra? (may seem really wierd but nice base defenisive stats with Eviolite is awesome. Once again probably outclassed by Fellicent but thought I would try)
Staryu? (With Blastoise gone this is the next best thing, Recover is awesome and Rapid Spin gives it great utility in conjuction with Eviolite and nice speed and isnt COMPLETELY helpless with 70 Sp. Atk like other Eviolite pokes
Lapras (Like a less bulky Walrein that can put offensive pressure on the opponent but I'd say outclassed by Walrein even outside of hail.
Omastar/ Omanyte: (Omastar has great bulk and decent typing with all the bugs in the tier but will be banned soon so Omanyte is a pretty good alternastive. All 3 hazards is awesome and gets Knock Off to fuck with other Eviolite users.)
Qwilfish: (Used it on a lot of teams and its typing is great and with Intimidate can set up a lot of hazards)
Mantine: (amazing special bulk and can check Yanmega and many special attackers)
Marshtomp: (I have seen this guy on a couple teams and shows promise, definetely should be used with Rest and Toxic considering no recovery and vulnerability to Toxic. It's typing is nice and gets SR iirc)
Ludicolo/ Lombre (nice typing and nice bulk makes them viable subseeders but is eaten alive by all the bugs in the tier)
Walrein/ Sealeo: (generally seen as a hail abuser but nice typing and noce bulk make it a potent overall wall)
Gastrodon: (will probably be moving up soon but amazing fro now in RU. You should know why by now; great typing, Recover, Storm Drain yada yada.)
Seismotoad (may be interesting but probably outclassed)
Frillish (Tried and is really good with Recover and its typing is amazing. Great bulk means it can take special hits all day)
Alomamola: (Really interesting, great physical bulk and HP and there a lot of Eviolite pokes that really appreciate the Wish.)
Fuck theres a lot of water types, Feraligatr poses a real threat with Encourage or DD and should be used more, I wann test out Wailord (Scarf Water Spout), Samurott and Simisear also seem somewhat promising.