In levels with layer 3 tides, the properties of the current normally apply to all swimmable areas, including bodies of water above the current. This patch restricts the pushing to the tide region, allowing water above it to be swimmable as normal.
Ah, much improved! It's a fairly simple patch when everything is said and done, but there's a lot you can do with it. I think a right-to-left water level with a tide that you can dip down into for a speed boost would be pretty neat, for instance.
Tested with Asar 1.81, Lunar Magic 3.21, SA-1 1.32, Snes9x 1.59.2.