I'd say the file "morewatr.zip" is a very good start.
I've heard people being happy about REP textures too, if I'm not confusing.
"morewatr.zip" was the set I was using back in my FS9 days. It was providing waves, but also and mainly new water textures and colors.
For waves only, I think there was an archive nammed "new_waves.zip" or something like that, with much higher resolution wave textures.
See what you can find from this page, make your tests
http://walhalla.mine.nu/fs2004/world.phpEDIT: here is morewatr.zip, try this first:
http://library.avsim.net/esearch.php?Ca ... DLID=43631