Hey Jon,
If I can quote the State of Maryland's Department of Natural Resources fact sheet on boat paint Just found this on the web, out of curiosity as to the qualitative "toxic" difference between hard and soft paints.
They say, "Hard paints contain varying levels of biocides, which are released slowly. Ablative paints generally contain lower levels of toxins, yet they are released at a more steady rate. The impact to the aquatic environment over time is about the same." That same fact sheet says that ablative "should not [and not 'must not'] be cleaned in the water."
This: Clean Boating Tip Sheet: Selecting a Bottom Paint http://www.dnr.state.md.us/boating/cleanmarina/guidebook/ts2bottompa.pdf
Not an easy issue, to be sure. Hell, I don't have goddamn holding tank! Oops. Well, we did poop on shore most of the time in sensitive areas (seriously).
Jud