Spearguns operate on the same principles as hunting bows, so why shouldn’t you be able to use a Bowtech underwater?
That’s exactly what the folks at Eastmans’ Hunting Journals decided to test in in their recent video. The underwater archer even demonstrates some reasonable accuracy by popping balloons with the arrows. As some commenters have pointed out, bows are not meant to be fully submerged or fired underwater. While we can’t think of any particular way this would damage your bow, it might not be a good idea to try it for yourself.