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.