That's a good idea. I bet when I'm rinsing it down, it won't significantly change the pH of the water below.
In the past five years, I've carefully re-arranged a few "artificial reefs" that I sunk under my dock to manage the water flow and provide shelter for the sea-life. I now have hundreds of Bluegill, Sunfish, and Pinfish (the water is brackish with a halocline that fluctuates throughout the day), as well as countless Speckled Trout, Red Drum, and Largemouth Bass hunting those smaller fish. Plus Turtle, Alligator, River Otter, Beaver, Raccoon, Fox, Bald Eagle, Barred Owl, Heron, Osprey that visit my dock regularly. In the late summers, I even have Manatee.
The only time I wash my boat with cleaning products is when it's on a trailer next to a wastewater sewer (vs. a stormwater sewer).