Life Belt

The Life Belt is an upgrade for Big the Cat in Sonic Adventure and Sonic Adventure DX. It is a green flotation device that makes Big automatically float on the water surface rather than sinking to the bottom. It also allows him fish while in the water himself. By holding the A/B button, Big will dive to the bottom of the water pond he is located in, but will float back to the surface, once the button is released

Location
The Life Belt is located in the Mystic Ruins' Adventure Field, and can obtained once Big has to enter the Ice Cap stage as it is needed to clear the said stage. It is located just before the entrance to the Ice Cap stage, where it can be found on the left side of the entrance to the room with the icy water pond.