Most (not all) no discharge zones are a crock brought on by environmental fanatics focused intently on minutiae.
Most marinas full of boats are actually hoes in the water that rarely move or get used.
Don't believe it, then just check out some marinas on a nice day and see how many boats are still in the slip.
As for the porta-potti, well enjoy yourself, unless you are in an area swamped with enviro-freaks and corresponding no discharge zones, a proper sea toilet with proper plumbing (note the word PROPER) is preferable to trying to balance your porta-potti while climbing up your companionway and over the rail or lifelines.
Its a shame that the environmental movement has been left to fanatics that principally want to control others rather than focusing on the chemicals that continue to be dumped into the water and in such quantity that you are now advised to limit your intake of quite a few fish species because of certain heavy metals.
I am perfectly aware that the majority of Wooden Boat aficionados are sensible folk. However, I need to point out that I am an amateur wooden boat enthusiast simply writing in order to try to help other amateur wooden boat enthusiasts. And while I take every care to ensure that the information in DIY Wood Boat.com is correct, anyone acting on the information on this website does so at their own risk.