Ok, Bluto is not correct here, and whether its out of ignorance or because he's a commercial captain and is trying to scare you is something I'd like him to address.
First, the situation he cites is EXPLICITLY covered in federal law. You are
NOT considered a commercial captain if you
voluntarily share in the actual expenses related to a voyage with people on board the vessel.
The key words here are
voluntarily and
actual expenses.
If necessary I will go dig up the CFR on this again; I have done a LOT of research on this matter, including discussions with the local USCG offices, the national USCG offices, my insurance company, etc.
BTW, this is NOT limited to things like fuel and food. As anyone who owns a boat knows, the cost of a "voyage" is VASTLY more than the fuel and food consumed. Engine wear and tear (ever price out how much per hour of operation those diesels cost you to own? You'll have a coronary!), maintenance budget, etc - all factor into it. You are being
extremely conservative with the law if you split fuel and food, and WELL within the "safe harbor", even if YOUR (as the owner) "out of pocket" appears to be zero - its NOT!
The other key, as I mentioned, is the voluntary nature of contributions. What you
cannot do is say to someone BEFORE going "that'll be $50 for your day of diving". That's a contract for carriage and you must be a USCG captain to do that, and if your boat carries more than six said revenue passengers, it must be inspected on top of it!
But there is
nothing wrong with coming back in after a day of diving and saying "we burned 100 gallons of fuel today, and the pier is currently charging $2/gallon for gas"; if the other four guys on your boat each then pull out their wallets and hand you $30, $40, $50 or whatever they want you are fine. Note that in some of these cases your actual "out of pocket" is zero - but your expense is NOT. Nowhere is it written that the expenses of the voyage must be EQUALLY split (that word is NOT present); just that whatever is contributed must be limited to the costs of the voyage
AND the contribution must be voluntary.
In other words, if one of the guys says "thanks for all the bubbles" and walks off, oh well. Your recourse has to be limited to not inviting him out again. Again - the key is that it must be
voluntary for him to contribute (or not.)
As soon as you do something that constitutes a contract for carriage (that is, you have a meeting of the minds, compensation and performance - in that order!) then you're in trouble. If you do the performance part FIRST, you cannot have formed a contract for carriage, as the fundamentals of a contract were not met. End of disucssion on that front.
Now, as to liability as a
private boat owner, you will be held to a reasonably duty of care
for the boat ride. If you run over someone with your boat and chop off his leg with a prop, you can expect to be sued (and will likely lose.) That's why you have insurance (and lots of it, when it comes to liability); boats can do a LOT of damage, in most cases, even for small boats, they are far more dangerous than a car in terms of their mass and therefore inertial damage possible. For example, my "big boat" displaces 25
tons. If I hit something with it, there's gonna be a
lot of damage. Many states (Florida included!) define a boat as a "dangerous instrumentality", just as they do a car.
The diving is another matter. As a "diver", you are just a diver. If you play "guide" (a.k.a. "Dive master"), then a whole different set of rules come into play, as with any professional. If you hold no professional certification then this is unlikely to go anywhere if someone tries to come after you. What is wise, however, is to be fully up-front with everyone who you take out as a friend what safety gear you have on board beyond the USCG requirements, WHERE IT IS, and what, if any, special knowledge you need to be able to use it, along with the fact that you're JUST A DIVER.
Start playing "tour guide" and you run afoul both of liability problems as a "Divemaster" AND you get nailed by the USCG on the charter ops! (There have been a few "fishing guides" who have tried to get around the rules on being a captain by charging only for their "fishing guide service", and "giving away" the boat ride. They lost.
)
Don't do that.
As an example, I have O2 on my boats. On the big boat I carry a DAN kit with two Jumbo Ds, fully charged, and a combo demand valve/non-rebreather setup. That's 2 man-hours of O2 at worst, and on the demand valve, depending on how heavily someone is breathing, it could be as much as 4 hours. Am I
required to do this by some standard of care? No, as I'm not an instructor or other professional. Do I want it for MYSELF if I screw up? Oh yeah.
Part of my standard "boarding lecture" to everyone who hasn't been out on the boat with me before is (1) where all the fire extinguishers and life jackets are, (2) where the liferaft is, (3) where the ditch bag and EPIRB is, and why it MUST NEVER be obstructed or blocked in, (4) where the O2 is. As part of that section I cover that (a) I ain't an EMT, and (unless I know otherwise) nobody else on board is either, and (b) anyone is free to and ENCOURAGED TO grab the O2 and use it at any time without prejudice if
they, in their sole judgement, think they need to; the first bottle is set up and ready to go, and refills are cheap enough that I am unconcerned about it.
As for marine insurance policies, have and use real marine insurance. The "good hands" type companies may consider someone bring a 6-pack of beer aboard or helping you to wash up "consideration." That's cra#. Read your policy, then fire the clowns and use a real company. Real marine insurance companies are clear that CHARTER SERVICE is not covered (unless you're paying the premium for same) and that their insurance binds you for RECREATIONAL service. That line is defined in federal law; stay well clear of the black-letter test and you're fine.
I do, however, strongly recommend that you carry LOTS of liability insurance; the most economical way is to get an excess-liability (personal umbrella) along with your regular marine insurance. Just make sure the umbrella will cover watercraft-related risks (some companies will, some won't.) You can easily get a couple million of umbrella coverage for a couple hundred bucks a year; most companies will require somewhere between $250,000 and $500,000 worth of underlying liability insurance on the risks involved (e.g. your homeowners, your car, your boat.) If someone gets seriously hurt that'll be the cheapest insurance you ever bought, even if you have absolutely ZERO liability at the end of the day (they are obligated to defend you if you get named, and as anyone who has played this game knows, the name of the game is to sue EVERYONE whenever there something goes wrong, and those who are not responsible almost NEVER get their fees back.)
BTW, IANAL. If you think you need one, you probably do, and the $100 you'll spend on a REAL opinion from a REAL one is well worth it.