It's understandable that it wouldn't be Thargoid, however I highly doubt it's aquatic origins.
Realistically, the sound file for the UA was make with a horn instrument slowed down with added synth sounds.
While it may sound whalish I don't think it points to whales.
It's more likely a race of tubas bent on destroying humanity with diseases and wasting our time with sound analysis equipment![]()
As a former tuba player, who's been carting our favorite space phage to every major system & brazenly entering populous starports and who's openly attacked Federation convoys traveling through Federation space, I resemble this remark.