Re: Host a Scientific Expedition!
"On a US boat in US waters, by law, enforced or not, you may not accept ANY compensation from friends or others for a boat trip. "
You're about 25 years behind the times on that. The USCG expressly clarified that standard that many years ago, and it was big and welcome news. Anyone who has been boating since the 80's should remember that clearly, unless they've already started losing their memory.
The way the law has stood since then, is that your FRIENDS may VOLUNTARILY contribute for food, fuel, etc. and even take the owner out to dinner. But that's all got to be entirely VOLUNTARY and NON-COMMERCIAL.
If you go around soliciting strangers to render some compensation and you have an oral contract that says they'll share expenses--that's no longer voluntary, no longer casual, and you're in business.
My vague recollection is that there was no change in the laws--just an edict from a more rational USCG Commandant, the same way that a similar edict recognized that 'securing' a dump valve in a no-discharge area could be done with a zip tie, no padlock required.
Enforcing or substantiating oral contracts is a whole other can of worms, and if you had such an agreement and the folks later said "Thanks for the ride, goodbye" without giving yu anything, you'd be simply SOL.