Rings of the fish help the player to breathe water, reducing any drowning damage. They are autocursing, meaning that whenever the player wears one it will become cursed, even if it wasn't previously cursed. A single blessed ring, or two rings of any other status will negate drowning damage. Interestingly, while it is identified as being rustproof upon greater ID, it is possible for one to be generated rusty; this behaviour was fixed in 1.2.0[1].