So if your on a dive say teaching and you do 2 dives as part of the class and something comes up say needing to free an anchor is it standard pratice for the crew to take the instructor and or the student down with them?
You're asking across a lot of legal terms here. A crewmember is someone who is "in service" to a vessel, as such, they are Jones Act mariners, and covered by maritime laws and regulations.
Sotis was on the call sheet that day as a safety diver, which meant that he was working for the studio and covering a required billet by the studios insurance company. I would imagine that the studio would take a very dim view of Sotis covering crew responsibilities as well as Studio responsibilities.
As Pete mentioned, Stewart was partway through his mod 3 rebreather class, and Sotis was his instructor for that class. I have no idea if Stewart was qualified to take the Mod III class (actually I have a very good idea, but I only have the handset downloads to go on), but that would make Sotis Stewart's instructor, which would be his third hat, responsible to yet another insurance company.
Get why this is so complicated? The reality is that Sotis and others had a duty to care for Stewart by 3 different masters, IANTD and their insurance company, the Studio and their insurance company, and the boat and their Jones Act insurance company. And every one of those folks wanted Sotis working exclusively for them.
As far as the boat goes, I'm pretty sure that there was no agreement between the boat's owner and Sotis to act as crew. But in going down to retrieve the anchor, Sotis placed himself in that liability.
So your question, would you take a student down to pull the anchor, has many answers, one being no. As a former nuke, I'm sure you can dream up some of the others, but they all end in no.
And by the way, we know that Stewart surfaced. It's pretty well accepted that the boat captain/crew has no responsibility for a diver diving, after all, they can't see them or have an effect on the outcome of any possible problem, but Admiralty court outcomes in the United States hold pretty carefully that once the diver is on the surface, they are a passenger again and that the crew does have a duty of care to rescue them. To make it more complex, Stewart and Sotis surfaced together. Sotis was closer to the boat, and so climbed the ladder first. No instructor does this with their student, but that's just my opinion that it's wrong. Sotis collapsed on the ladder, taking everyone on the boat's attention away from Stewart for a crucial short period of time, and in that short period of time, Stewart disappeared. For fun, read the Becky Bryson incident in front of the admiralty judge in Virginia. Becky was by all accounts a good captain (and a friend of mine, although that has no bearing). A diver surfaced in distress behind her boat and the crew failed to render effective aid to the diver resulting in the diver drowning. Becky was completely at fault in the opinion of the administrative law judge, and had her license revoked.
Becky's lawyer at her hearing was the diver who recovered Stewart. Because we can't have enough drama.