It doesn't quite work that way in the USA, but it's not cut and dry either.
In order for someone to claim negligence against you, there are four criteria that must be met:
1. There existed a duty to act.
2. The duty was not fulfilled.
3. The circumstances that led to the breach of duty were foreseeable and/or preventable.
4. The breach led to or exacerbated an injury.
A recreationally-trained (non-pro) diver has no duty whatsoever to assist in an emergency. They can legally refuse to do so. However, if they do choose to help, they voluntarily create a duty, and are held to a "reasonable standard of care" based on their highest level of training ... in other words, what would someone at that level of training reasonably be expected to do.
People with professional level training (DM or above) are held to higher standards, and have an implicit duty to assist in an emergency. They are, however, still held to the standard of "reasonable care" for what they were trained to do.
... Bob (Grateful Diver)
(Edit: Ah, I posted before reading the preceding post. I suppose repetition doesn't much hurt in this case).
Bob -I am going to disagree with you here, but it could also just be how it is typed. Just because I am a professional, I do not have an implicit duty to assist in
every emergency. To be more specific, I
DO have an implicit duty to assist with anyone under my duty of care (i.e. someone with whom I have an agreement to act as a professional). I
DO NOT have an implicit duty to assist in an emergency for some random person on the dive boat.
With that said, if I am in a position to help, I am going to help to the fullest extent of my abilities. Let the chips fall where they may afterwards. Also, getting out of the way because someone else is executing the rescue is an excellent form of help.
------On to a different topic...
In terms of letting the boat crew know my highest certification and the concern about being paired with an inexperienced diver, I approach it a few ways....
1) If it is a "once in a lifetime dive", I am not going to leave it to chance. I will have a pre-determined buddy or I will hire a DM to be my buddy. If the DM is my buddy, then I will make sure with the shop/charter that no one else will be paired with us.
2) If it is a dive where I am going to be happy breathing compressed air at depth, then I really don't care if they buddy me with someone inexperienced. Yes, I have had the 15 minute dive and got back on the boat with 2300 psi because of my insta-buddy. It is a risk one runs when signing up for a charter alone.
3) In regards to the "lying" form, I put down the highest level of certification that I can prove (with the cert card) at that moment. I have also learned that many charters cringe when they see a DM or instructor card. Their side of the story is that too many "professionals" feel like their certification card allows them not to follow the boat's rules or guidelines set forth in the briefing.