Seaking

The fact that Seakings stats are underwhelming, and Seaking doesn’t have any utility, makes it a wonder why we even have an overview for this mon. Sure, you've had Kyogre, and you got your Vaporeon, Gyarados, Suicune, Milotic, Sharpedo, and Golduck (who has higher total stats), but if you haven't tackled a legendary raid with a team of Seakings, well, are you even a Pokemon master?

Best PvE Offensive Moveset

• Waterfall is a fine move for Seaking with STAB.
• Poison Jab is superior to Peck for damage output.
• Water Pulse is Seaking’s only charge move with STAB.
• Ice Beam is slightly superior to Megahorn for the faster charge time and type effectiveness.
• Icy Wind and Drill Run, Seaking’s legacy moves, are not powerful and offer no synergy with Seaking.

Best PvE Defensive Moveset

• Poison Jab is superior for counter coverage against Grass and Electric-types.
• Ice Beam and Drill Run are Seaking’s strongest defensive charge moves due to counter coverage.
• Megahorn takes too long to charge relative to Seaking’s poor defenses and Icy Wind has too long of an animation time.  
• Water-type moves like Water Pulse and Waterfall offer no advantages on defense.

Seaking's optimal moveset requires legacy moves (now accessible via Elite TMs). It is not recommended to use Seaking without this moveset, even when considering the cost effectiveness of Elite TMs (meaning there's better Pokemon to use Elite TMs on).

Poison Jab features average damage output and superior energy generation, letting Seaking access its charge moves sooner. Waterfall is powerful with STAB, but slow on energy gains. Peck has inferior stats. 

Icy Wind isn't particularly strong, but threatens Grass-type counters, and the guaranteed debuff against the opponent can become oppressive over time. Ice Beam and Megahorn are stronger, but both demand more energy and don't provide any debuff value when shielded. Drill Run is Seaking's best charge move due to its lesser energy cost, despite the lack of STAB, and provides valuable coverage. Water Pulse is the ironically the least impressive charge move available, requiring the most amount of energy, but falling behind in Damage Per Energy (even with STAB).