Shoal (The Underwater War)
From Tardis Wiki, the free Doctor Who reference
The Shoal were a fish species who communicated by colours of the skin as a sign of emotions. They lived in underwater cities. They were 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 Shoals 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)