Light Ring

Light Rings are found in various locations in the Great Sea in The Legend of Zelda: The Wind Waker. Using his boat, The King of Red Lions, and the Grappling Hook, Link can fish at the bottom of the ocean at the spot indicated by the ring of light, usually finding treasure there.

Appearance
The light rings appear at different places all over the Great Sea, usually at night. Due to their brightness and contrast to the surrounding ocean, they can be spotted from very far away (especially at night) with the Telescope. The light rings fade when Link gets within a certain proximity, but a "shining" sound persists and grows louder as Link gets closer to the sunken treasure. Finding the chest usually boils down to trial-and-error, and if you lose track of where the light ring was, sailing away will make it reappear.

Treasure Charts
When a Treasure Chart or a Triforce Chart is used to find treasure, the regular small circle of light is replaced by a tower of bright light that can be seen from very far away (and even over obstacles). This light will still fade when Link gets close, but it's more attention grabbing in the first place. This, in addition to the map accompanying each chart, makes the treasure easy to find.