It seems that Vanish is interfering with Fishing (by ColonBlow). It'll work on rivers but not open water bodies - and it doesn't happen on every server. All I can pass along is that with Vanish things are screwy (likely calls using the UnityEngine.LayerMask.GetMask("Water") thing in the api because the Fishing plugin can't "see" the water using Physics.Raycast(player.eyes.HeadRay()) -- removing Vanish results in Fishing working properly again.

Don't know what Vanish is doing that would cause this behavior but it's likely not intentional. Thought I'd pass it along.

so you are saying that you can't "fish" while in vanish? or fishing does not work regardless of being vanished or not ?

Right. Regardless of being vanished or not -- OR if you're authlevel 2 or not -- fishing in open water (offshore ocean, lakes, etc.) returns an error from the Fishing plugin that says the player isn't looking at water. Spear fishing works when it wants to but it's still the same general problem as the detection isn't working correctly. Fishing with a pole or a spear in a river, however, works if the water is deep enough (more than knee-high) which isn't normal behavior for Fishing (and the same problem in the case of spear fishing on shorelines).

Removing Vanish corrects all of the above and remains corrected through disconnect/reconnect and server restart.