Game Mechanics: Inability to attack swimming enemies

[Rainflush]

If for example an enemy flees into water (such as the various crocodilians in the Oasis of Marr) I won't be able to hit them with auto-attack shortly after they begin swimming. It says "You cannot see your target".

I'm not sure if this occurs when both opponents are entirely submerged (as would be the case in Kedge Keep, for example), though it makes fighting around water rather frustrating at times.

Does anyone else have trouble with this?