Had a random thought about a move that I think doesn't see the light of day (usually) and ran some calcs...
~Set has 148 evs in Hp, 172 in def, and 186 in sp.attk. Haven't seen that ev spread for vaporeon before but it's listed as 'common.' The original set for vaporeon with these Evs has the moves: Scald, Icy wind, Ice beam, and Muddy water.~
0+ SpA Vaporeon Synchronoise vs. 252 HP / 0 SpD Toxapex: 80-96 (50.9 - 61.1%) -- 94.9% chance to 2HKO after Black Sludge recovery
186+ SpA Vaporeon Synchronoise vs. 252 HP / 0 SpD Toxapex: 94-112 (59.8 - 71.3%) -- guaranteed 2HKO after Black Sludge recovery
186+ SpA Vaporeon Synchronoise vs. 252 HP / 252 SpD Toxapex: 78-94 (49.6 - 59.8%) -- 84% chance to 2HKO after Black Sludge recovery
With that spread, perhaps a moveset of Scald, Protect/Heal Bell, Wish, and Synchronoise could work if your team dislikes Toxapex.
Bruxish gets the move too but psychic fangs is way better for it from what I can tell. Sadly no poison types get Synchronoise and the only other water type that has access to the move is Golduck.