OpenWaterESP is a Minecraft hack that shows whether the user is fishing in open or shallow water, and therefore whether or not the user can receive treasure items from fishing.

OpenWaterESP also draws a box around the exact 5x4x5 block area that Minecraft uses for its open water calculation. The box is green whenever the bobber is in open water, or red and crossed out when the bobber is in shallow water. This is useful for debugging fish farms, as it makes it easier to determine which blocks are preventing a broken farm from passing the open water check.