- You may be looking for the fishmen of Kandalinga.
Some of the fish people had scaly skin, large, fish-like eyes, gills and fins. Others had undergone only partial conversion and resembled humans with gills and goggles to protect their eyes. (TV: The Underwater Menace)
The fish people regularly invited River Song and the Doctor to their annual parties. On one occasion in which they accepted, they were dipped in guacamole and tied upside down over a fire pit. After this River dubbed their invitations a trap and always sent them a decline.
Sometime later, upon receiving another invitation, the Eleventh Doctor wanted to attend one of the parties against River's advice. Once again, they were dunked in guacamole and tied upside down over a fire pit while the Doctor mused about how fish people could know so much about guacamole. (COMIC: An Adventure in Brine and Plaice)