Technically, no the OCEAN doesn't, but reefs definitely do get a WC, fresh SW is brought in and currents and wave action push water full of waste it toward the shore where it gets "Skimmed" persay or fuels algae. Or it gets taken out to deeper waters where there are a lot of methods of things getting removed ... if you take a square foot of Reef and say open a small bottle of food colouring over it, it's going to disappear, QUICKLY, the coloured water is exchanged with fresh salt water from the currents. Therefor the reef itself is under a constant water change. Water is constantly moving removing waste from corals and constantly supplying fresh elements. We can't replicate this in our tanks so we make up for it with equipment and water changes.
Anyway, best of luck on your setup, I highly advise you stay clear of any chemicals, especially Hydrogen Peroxide of you want to stick to the no WC approach.
Happy Reefing!