Additionally, Remoraid is possibly in part based off of the Archer Fish, which is known for shooting water (to knock prey off branches and into the water), and octupi are known for shooting ink, making them both aquatic animals known for shooting projectiles (further backed up by the gun/tank theme in their beta designs).
Although if you ask me, they really should have changed the designs a bit and switched which one was evolved and unevolved, because octupi are lame and just use their projectiles to flee like the cowards they are, while Archer Fish are cool and smart enough to realize that they have access to a real-life Hydro Pump (or at least Water Gun), so of course they’re going to be sweepers and use it to hunt.