Shoal (The Underwater War)
From Tardis Wiki, the free Doctor Who reference
The Shoal are a fish species who communicate colours of the skin as a symbol of different emotions. They live in underwater cities. They are divided between 'the low swimmers', 'the medium swimmers' and 'the high swimmers'. The low swimmers had a white globe, which they could use to stun other Shoaly or even kill them. The fish creatures had also fashioned a forked weapon as protection.
Their home planet was Hydron and the capital city of their planet was Reef. They used underwater roads to travel above the water beds. (NSA The Underwater War)