"STARBOARD!"
A rule of sailboat racing is that in open water, boats on port tack (wind coming from the port side) must give way to boats on starboard tack.
When you've got a massive great sail stopping you from seeing all around you very effectively, shouting "Starboard!" at the top of your voice is often the best way to get the attention of the other boat.
Shouting really loudly helps. Shouting "port" loud enough as if you know what you're doing might just work...