Look at the back of a 'toon set up for fishing. They'll generally have circulating water through a tank or 2 on deck (live well/bait), use a bracket on the back of one of the pontoons to simply hold a hose stuck in the water, held below the surface. Pretty simple once you figure out what you're looking at. The pressure type pump can use something very similar, but it's going to need a filter to make sure it doesn't suck up a piece of crud located somewhere between the source and the pump. That will cause it to stop working until you to clean it, likely about the time it's least convenient.
Check out RV sources for a pump and filter. They use the same setup, the difference being they pull water from a tank.