PSD diving is totally different then rec or tech diving. I'm a very experienced recreational diver and have dived in enough challenging conditions - crazy currents, caverns, etc. The PSD team that I joined last summer is on the Hudson River in NY. Current, black water, lots of entanglement hazards, a good number of our calls are for bridge jumpers. The part that I've yet to get my head past is not all that stuff but the fact that as a PSD diver you're not in control of your dive and I've always had an issue with needing to feel 100% in control and responsible for myself when it comes to diving. At least the way we do it in the conditions we have, you're relying on your tender to send you to the right search area, give you the correct signals (and sometimes with consideration for the time it will take you to set yourself up to respond), and you have to trust that the tender is going to understand and take proper action to the signals you give on the line as well. We do have comms but we rely more on the rope signals because comms will and do fail. I'm still working on the diving but I'm completely happy being part of the team as a tender and EMT as well. Both of those roles are just as and sometimes more important then the diver. Everyone on the team is critical to a successful operation.
If you do decide to join a team, check them out first. PSD requires good training and a team that wants to be ready to answer the call needs to drill, drill, drill. We're out one evening a week, regardless of the weather.
A good book to get an idea of what's involved in PSD is Public Safety Diving by Butch Hendricks (of Lifeguard Systems)
Public Safety Diving
And like someone already said, if you do try it and decide it's not for you, don't do it. I've seen guys with rec and tech certs out the wazoo gear up, jump in and call it a day. Any good dive team leader and members will not give you a hard time or push you if they feel you can't do it or it's not for you. If you decide not to be a diver but still want to be involved, many teams like to have dedicated tenders. That could also be an option. (Some teams also start you as a tender and have you do a lot of the tank changing, gear maintenance, gear checks, etc., before they consider letting you try diving.)