GURPSよろず

　Creatures that communicate via ground vibrations use 「低周波会話」 (「低周波会話」p. B89), while underwater dwellers often have 「超音波会話」 (「超音波会話」p. B94). Remember that 「低周波会話」 includes Subsonic Hearing and 「超音波会話」 includes Ultrahearing.
「水中会話」 (p. B87) is fundamentally unrealistic, but widespread among aquatic supers and fantasy races (e.g., “Sea Elves”).

■代替案（Alternatives）
　Being able to speak in the frequency range used by a particular beast doesn’t confer any special ability to mimic or communicate with it; those abilities are 声まね (p. 161) and 「動物会話」 (p. 77), respectively.
For other forms of communication inaudible to normal humans, see 「遠隔通信」 (p. 81).

■パワーアップ（Powering Up）
　Any of these traits would be reasonable for an elemental Sound/Vibration power --or 「サイコキネシス」, if it lets the user create and modulate vibrations.
「水中会話」 also suits waterrelated super-powers, divine powers bestowed by sea gods, and spirit powers that influence naiads, undines, etc.
才能 adds to all IQ and Hearing rolls to understand speech or be understood when using speech-related abilities.