The Survival. The Primordial Beast. The Gill-Man. The Deep One. There's a lot of analysis that could be done here, but bottom line? Big fish in deep water are scary and there's a part of our monkey brains that has never forgotten that fact.
Since this is a tropical monster, I went with a tropical, vaguely lionfish-inspired color scheme of teals, bronze and copper. Might not be a *perfect* fit for my Early Modern Monster Hunters project, but it's a great Universal monster--and Solomon Kane *did* spend most of his time in the tropics.