We are Scuba divers and snorkelers and use our TI as a dive boat all the time mostly in South Florida and the Florida keys (where we live).
We have our TI specially hardened for offshore use. It's actually pretty easy to get on and off the TI by climbing over the AMA's and onto the tramps. The tramps are a must have for diving.
Watch this video and if you have any questions fire away, we have gone out several times with 4 divers, each with 2 tanks (that's 8 tanks plus all the gear like BC's, weight belts, and dive fins (which are huge), along with coolers with enough food and beverages for the day. We Lobster and spear fish in season, and have even loaded the boat down with as many as 10 crab traps stacked on the AMA's.
We no long have our Sea Ray powerboat so we use our TI for pretty much everything we used to do with the Sea Ray, we are out every single weekend all year round with it. Yes down in Key West you can get on dive charters but they typically cost about $100 bucks a person, or you can rent a power boat (we do sometimes), but that's typically between six hundred and a thousand bucks a day, plus you can easily go thru $200-$300 dollars in fuel (that's why the boats have 60 gallon tanks LOL). The main reason we sold our powerboat was because dry storage down here is around $400 per month (ouch).
It cost us nothing to store our TI (we keep in in our garage), maint costs are maybe $50 bucks a year for rudder pins and that's about it. Our TI gets about 100 mpg fuel economy so we can go out all day for about a dollar in fuel.
If your diving off the boat the single most important thing is a very good anchor (we have had our TI take off on us before while diving without good anchors). My anchor system is totally automatic and is never removed from the boat ( I have 150 ft of anchor line). Actually nothing is ever removed from the boat (actually I don't recall ever removing the motors), it's just stored on the trailer as you see it in the video with the AMA's folded in, and the sails laid down on top of the hull in the garage and that's it, only takes maybe 5 extra minutes to launch over most other TI's. https://www.youtube.com/watch?v=2BcdE0137Xk
I'm sure you could do all the same with an AI.
Yea we have that rope ladder but nobody bothers to use it, they all just climb up over the AMA's, we usually remove our BC's and just float them, climb in the boat then drag them aboard.
Storing all our gear (tanks, bc's, coolers, etc) in a tow behind inflatable raft is the easiest solution, by doing that we can easily carry 3-4 people on the TI.
Hope this helps you
Holy crap I didn't realize this thread is from 2006, I'm sure all those kelp beds are all dead and gone by now (LOL, like our coral reefs...)