Doesn’t matter if a boatload of Captains is out on the water and the “Captain” screws up and runs it aground. There is ONLY one captain aboard to call for abandonship. or firefighting.
Of course if the ship is going down, and in my judgement I ‘may’ have to hasten preparations to do something, I may. But legally there is ONE master in charge.
If you are aboard a yacht as a guest, then you are not bound by anything other than the ‘good samaritan’ rule. If you are aboard as a ‘helper’ then you are subject to having seamanship decisions scrutinized. If you are in doubt, bring a box of crackers and cheese with you. Let it be known that you brought a snack for everyone. That way you are a ‘paying guest’ which changes everything as far as your status. If you bring lunch aboard, you change the trip from a helper to a passenger. You just have to make it obvious that the food is for everyone, not just the ‘Captain.’