Not to be the downer here, as I have often also thought about the variety of stuff to do on scuba for people, but for the most part it doesn't sound worthwhile, unless you find a good niche (location, deep pockets, not a siff marina etc.)
Over and above that (I may be wrong), but it really sounds like you have only just started diving? Correct me if I am wrong, but I will continue non the less.
If you have only just started diving and you were saying you want to do basic level 1 or something? Not familiar with that (I am only a PADI peep
...but does that mean you are not even certified yet? If so I would strongly suggest not pursuing what you intend...even after you are certified or have a couple dives under your belt. It is one thing if you have your gear on a boat and a friend drops his phone, and you go...well, it's within my cert limits, I have enough air, etc. etc. and basically plan the dive like a normal dive. VS. Let's drop into a busy marina, with murky water, entanglement possibilities everywhere, never-mind the traffic and risk there and so forth. Accidents happen very quickly and start with the smallest things, that build and cause other problems. Normally things go well, but I sure wouldn't want to be in a bad situation, that I hadn't planned atleast a little bit for, never mind needing the experience for.
I might of read this situation completely wrong, but I rather be the one stressing caution compared to rambo'ness
Rather get the correct commercial training if it is something you want to pursue vs. Just quickly helping a friend find a phone.
Good luck, and let us know how it goes.
Over and above that (I may be wrong), but it really sounds like you have only just started diving? Correct me if I am wrong, but I will continue non the less.
If you have only just started diving and you were saying you want to do basic level 1 or something? Not familiar with that (I am only a PADI peep

I might of read this situation completely wrong, but I rather be the one stressing caution compared to rambo'ness

Good luck, and let us know how it goes.