nice find, hans! i will give it a try too!...already spend days on this. so, whats a night...
and i guess, the pic is not read well when resized, cause of a fixed defined size somewhere in the dat. so the game looks for a 512x...and therefore cannot read a 1024x...but thats just an idea.
update:
i think the mesh of the water is defined with a 512x... texture. so the game exspects a 512 texture. dont know where to look for this data. EnvSim.act hasnt it stored.