This mod changes some of the controls, while you are on a boat.

R - is not changed to switch between driving and fishing on a boat.
W - is now a toggle to go forward at full speed if you are driving a boat.
P - shows the radar while you are fishing on a boat.

While driving and the boat is moving, using the R key switches into fishing mode and the boat still goes forward in trottle speed (this is also original in the game).

You need the Unity Mod Manager from here:
https://www.nexusmods.com/site/mods/21

Then install my mod from here:
https://www.nexusmods.com/ultimatefishingsimulator/mods/4

Start the game and make sure the mod is "green" (enabled).

p.s. Not sure, but I guess it is best to have the game installed into: C:\GOG Games\

pps. before you update the game, open Unity Mod Manager and uninstall -> update the game -> install