Empoleon and Gyarados would be prime candidates, both being water types with Trident-like head decoration.
Additionally, it would make sense to add it to other fierce looking water types or ones with weapon connections (Cloyster, Sharpedo, Crawdaunt, Samurott, Clawitzer, Golisopod, Drednaw, Barraskewda, Basculegion, Veluza) as well as some others that are connected thematically: Eelektross (fierce looking "fish" whose electric type fits the Channeling enchantment), Hydreigon (three heads) and Dhelmise (shipwreck -> tools lost underwater).