New Oceana
From Tardis Wiki, the free Doctor Who reference
New Oceana was a colony planet that, at some point, had been entirely flooded due to rising sea levels and catastrophic global warming. A nomadic race of amphibians later inhabited the planet.
The planet also had many thriving species of fish, including some larger fish resembling sharks.
The Twelfth Doctor visited New Oceana on a tour ship. (COMIC: Beneath the Waves)