Personally, crabsquid and sea dragon are annoyances, the ghosts are bros, and the reaper is scary.

For me, the reaper is just uglier then scary. Ghost leviathans are cute and crabsquids are just dumb

The Crabsquids are annoying if anything

The only thing scary about Sea Dragons is their roar

The Ghosties are cutie-pies (shoutout to my boy Jeremy in the Lost River, always hanging out near the Gargantuan skeleton)

The Reapers are a nightmare: there's a lot of them (25 iirc), they're always hiding in dark water and their roars are are just awful, they're the only thing in the game that i'm actually terrified of