I said I'd answer questions, not write tutorials!
I'll point you in the right direction though.
In the OLC GUI Special folder find and edit maps.cfg. Also check the 'Sea' and 'Submarine' folders... you'll probably want to delete those folders.
Or you could just use OLC GUI 1.2.6 instead. It doesn't have the realistic map updates bit, but it also doesn't have the zoomed-waves fix.
HTH
OLC