I don't see why you can't do the cam break-in on land, the engine isn't under load and should have enough water to cool it from the muffs. I like to see a bit of water being pushed past the muffs while operating the engine. IE: the hose is pushing more water than the engine is drawing.
For cam break-in - 15-20 minutes at 1500-2000RPM. Fire it up and immediately take the engine to 1500-2000RPM, no idling until the cam is broken in.