Better than spilling bleach into your local waters:
*Buy a snorkel, mask, and fins.
Also, buy 3M "ScotchBrite" dark green plastic scrubbers and a plastic putty knife/scraper.
During my short stint working on a megayacht, I used to clean the dinghies (23' Parker and 21' Novurania) with the tools listed above.
Using this technique took me approx an hour to do a very good job on each boat. It's worth the extra effort to protect the environment
and keep the water clean for all of us to enjoy.