Bubble ring

A bubble ring, also known as a Water Ring or simply a ring, is an underwater object appearing in Super Mario 64 and its remake, Super Mario 64 DS.

Super Mario 64 / Super Mario 64 DS
In Super Mario 64 and Super Mario 64 DS, bubble rings are seen only in the ninth course: Dire, Dire Docks. When Mario, Yoshi, Luigi, or Wario swims through a bubble ring, it replenishes two wedges of his Power Meter, and a number appears above him. This number represents the number of bubble rings the player character has passed through. When the player character swims through five bubble rings, he is granted a Power Star.

Bubble rings are required for the fourth and fifth Stars in Dire, Dire Docks. In the fourth mission, Through the Jet Stream, the player character must swim to the other side of the tunnel to find a jet stream spraying out bubble rings. After the player character collects five of these bubble rings, a Power Star appears above the jet stream, and Metal Mario or Metal Wario can collect it. In the fifth mission, The Manta Ray's Reward, the player character finds a Manta Ray swimming around underwater and leaving a trail of bubble rings. The player character must follow this trail to collect five bubble rings and make the Power Star appear.

Mario Party 4
In the Mario Party 4 minigame Manta Rings, rings appear along with a gold type created by a Manta. The blue rings are worth one point, and the gold rings are worth three points. In this appearance, the rings are composed of bubbles.