Shadow Blastoise

The introduction of its Shadow form finally put Blastoise on the map. However, not everything on a map is worth visiting! Shadow Blastoise has a general performance fairly close to normal Swampert, so it's really nothing special for the most part.

Best PvE Offensive Moveset

• Water Gun sports higher EPS and better synergy with Shadow Blastoise' best charged moves, therefore it is marginally better than Bite.

• Hydro Cannon* is objectively outstanding. Don't bother with other options.

• Hydro Pump is Shadow Blastoise's optimal non-exclusive charge move.

• Ice Beam has its select advantageous matchups.

• Flash Cannon is an awful 1-bar charge move, and Skull Bash isn't useful either.

Best PvE Defensive Moveset

• Water Gun hits a little harder than Bite thanks to STAB and also gains energy faster, but Bite has wide neutral coverage that leaves Shadow Blastoise less of a sitting duck against Grass types. Overall, Bite has a slight edge.

• Hydro Cannon is a fantastic choice for power and pairs best with Bite, while Ice Beam is perfect for counter-coverage and works just fine with either quick move.

• Hydro Pump hits hard and early in the animation, but Shadow Blastoise may not live to use it.

• Even when Hydro Pump is resisted, Flash Cannon is still worse.
• Skull Bash takes too long to access as a 1-bar move, and is harder to dodge than other moves. 

Water Gun performs better than Bite and also gets STAB. 

Behold, arguably the best charge move in the game: Hydro Cannon. This is the main highlight of Blastoise, and is almost mandatory if you want Blastoise to perform at its peak potential. Hydro Pump is a lot slower and less efficient in comparison; if you're gonna use Blastoise then trade for one with Hydro Cannon, or don't use Blastoise at all. 

Ice Beam should be the second charge move for Blastoise as it provides meaningful coverage. Flash Cannon can hit hard, but with a 65 energy cost it's quite slow and doesn't really complement Blastoise anyways.