What if Reefbacks sounded like this when you got close, as if they were trying to talk to you

TacticalHog

the current Reefback call is amazing, and fits the creature well, but I think if you get close, it should sound like it's scanning you with echolocation, or even trying to communicate with you.

Isummon_Durt

Sounds good to me. Reefbacks already look reminiscent of the cool bioluminescent creatures from The Abyss. Although realistically, I doubt that they'd be able to extract enough proteans from the water to have advanced brain-body mass ratio to have communication... but could be a cool effect, nonetheless.