Aqua Goomba

Aqua Kuribō (アクアクリボー) are enemies that appeared in Super Mario Land 2: 6 Golden Coins. They are Goombas wearing a diving helmet. In the final level of the Turtle Zone, several Aqua Kuribō are found in the belly of the giant whale. Despite their name and appearance, they generally appear free from the water and will behave largely like regular Goombas, with the only difference being that jumping on them will propel Mario upwards with greater force than a standard Goomba and they will not be flattened.

Aqua Kuribō are very similar to Goomdivers from Mario & Luigi: Superstar Saga, which may have been based on them.

Trivia

 * Aqua Kuribō is a play on Aqua Mario 「アクアマリオ」, a term used for underwater Mario in the game's manual.