Just open the client exe up in your hex editor
search: 8B465099B906000000 and replace with 8B465099B9FF000000 you will find this in 3 places so change it all 3 times. Then save the exe.
Next open the .rsw file of the map you want to change the water type and look at line 000000A0 in the rsw of the map it should look somthing like this :
0000 0000 0000 0000 B841 0000 0000 0000
the 2 00's after B841 that is water type max you can do is FF which is 255 but lets say we want to change it to 7 It would be changed like so :
0000 0000 0000 0000 B841 0700 0000 0000
Then all you have to do is add the water texture to the right folder
data\texture\¿öÅÍ\
and the water's type 7 so the jpg's for that type would be named
water700.jpg - water731.jpg if you miss any of them you'll get an error so make sure you dont forget any.
Also the regular water types are 1-5
00 - Normal light colored water (Prontera)
01 - A little darker water
02 - Very light/tropical water (Jawaii)
03 - Very dark water (Culvert)
04 - Lava (Magma Dungeon)
05 - Dark/muddy water
Just incase you need to know the orignal's
I would attempt to translate this to german but its better if someone that knows german does that x.x anyways enjoy.
example:






