Gastrodon - West Sea

On April 30, 2019 Niantic released both variations of Shellos into the wild, probably by accident, and then quickly disabled their spawns. A few weeks later on May 17, 2019, Shellos was officially released into the game and Gastrodon no longer was one of the rarest Pokemon. For all this craze and excitement, Gastrodon unfortunately is somewhat of a disappointment for PvE, as it doesn't have the stats needed to perform as well as other options. It could be an okay gym defender, but easily loses to Grass-type attackers. 

Best PvE Offensive Moveset

• Mud Slap performs better than Hidden Power, even if the latter would get STAB. 
• Earth Power pairs well with Mud Slap and fulfills a Ground-type role.
• Not only is Earthquake a very rare legacy option, but it also performs worse than Earth Power. 
• Water Pulse and Body Slam are bad for offense. 

Best PvE Defensive Moveset

• Hidden Power can offer some interesting coverage if you get lucky, and also gets slightly more defensive energy gains than Mud Slap.
• Body Slam is the most difficult to dodge and can be spammed.
• Water Pulse has an earlier damage window than Earth Power, but doesn't hit as hard. 
• Earthquake sucks for gym defense since it's very easy to dodge. 

Mud Slap has superior parameters to Hidden Power and benefits from STAB.

Body Slam is Gastrodon's cheapest charge move energy-wise and can be used to bait shields and apply pressure. Earth Power takes advantage of STAB to deal big damage if unresisted. Water Pulse is slightly underwhelming, but can hit some targets that its Ground and Normal-type combo cannot hit, as well as doing more damage to Flying-type Pokemon. Earthquake is Gastrodon's most powerful move, but it's too unreliable compared to Earth Power.