To add to Eric's post, I believe the USCG PFDs also have to be "readily accessible" if they aren't being worn. So you can't shove them down into the hull and screw the inspection port back on... Oh, and anyone under 16 must wear them at all times outside of an enclosed cabin.

At least from what I understood from the marine patrol dudes who checked out my boat.

I was on the way back from a race day, and still wearing my pfd which (luckily) happened to be USCG approved (type II I think... Didn't have the floating pillow to keep my head upright while unconscious) when their RIB pulled out of the inlet and "chose" me to saddle up to. The crew had on those inflatable pfds.

I will say they were generally courteous and allowed me to put out a fender before they slid up against the hull. They didn't get on the boat (I think they were a little confused by the nets on the amas) but asked for all the usual paperwork and asked about the pfds. I had a pack of them sitting on the bench seat in the cabin so it was easy to reach down and grab them.

So yeah, two of my flares were out of date, and it "would be helpful" if I had a radar reflector, but I had all the daytime signal devices (mirror, floaty-tube, dye) and some strobes (not SOLAS but close) so they cut me some slack.

They said they stopped me because my registration sticker was on the wrong side of the boat (port bow if you must know...)