It does contain harmful compounds. It wouldn't work to prevent growth otherwise. You use a random orbit sander hooked up to a shop vac just like when you sand anything else (unless you prefer dust going everywhere).
For a 40' sailboat it doesn't take multiple person days, it takes about a quarter of a person day. More if you really have to take off a lot of layered up material. And you're right, blasting would work better in that case.
> It does contain harmful compounds. It wouldn't work to prevent growth otherwise.
Nowadays there exists bottom paints such as polysiloxane based ones that work by creating a very hard and smooth surface that critters find it very hard to attach to, rather than poisoning them.
There are levels of toxicity. For some old paints, allowing the dust or run-off from pressure washing to touch the ground would be violating some regulation. Removing those old paints is more complicated. They need to be removed completely and cleanly, so sanding is a bad choice.
This isn't the case for any paint now purchasable, but most still contain biocides that you want to avoid for your own health when cleaning or sanding.
