Thanks for all the information and tips so far!
In regard to the tipping and the sheet, do you break up the tips in little piles, so much for this person, so much for that person or do you total it all up and leave one amount and it get's divvyed up to them by the resort? If it's a single total can you use a credit card, add it to your bill or do you have to bring cash?
My memory is that the day before you leave, they will drop off a bill that reflects your drinks, any rental gear, trips taken, etc for the week so you have time to check it over and make sure it's accurate. They will also drop off a tip sheet that shows the different categories of employees and you list how much you want to tip for each category unless you're going to pay cash. Maybe you write in the name(s) of your dive guides/boat captain and/or fishing guide, I can't remember.
Then you drop by the office that afternoon and settle up. Any drinks you charge after that you pay for the next morning before getting on the boat.
Because you'll develop a more personal relationship with your boat captain and dive guide, you might want to do as I do and give those guys cash because as someone once put it, "Cash is always mo' better" and put the other tip(s) on your credit card. On the other hand, cash is a precious commodity when you're in a foreign country so feel free to put it on the card if you prefer. I talked to them about it once because there was a very old review on Trip Advisor that said there was a rumor the employees didn't get their tips if you put it on the card. They were surprised to hear that and assured me that they didn't think that was ever the case.
You'll have the same boat captain and dive guide all week. Brad and Marcel like to switch off, so one week Brad's the captain and Marcel's the guide, then vice-versa the next. On the other boat, John doesn't like to scuba so he's the captain and Daniel's the guide. All four are great. John is somewhat shy and his accent is really thick, so he doesn't talk a lot unless he's had a few beers in which case you can't shut him up, lol. He's also as big as a house, so he's a bit intimidating but he's really just a big teddy bear. Usually there's only one boat used for the night dive since only a couple of divers are interested, so the two crews take turns doing that.
Back to cash, one really nice thing about staying at TIR is it's paid for 45 days in advance of you setting foot on the island. Assuming you're flying in just before you get on the boat and flying out the same day you leave the island, you don't need to bring a lot of cash with you. Tips and incidentals, that's about it. Don't forget the $35 exit tax at the airport, lol. I heard they used to require cash (!), but now you can put that on the card, too.
If you're really going to be hanging around the Radisson rather than the Princess Marina for a couple of hours, you'll be close enough to the core of the city to go take a look while you're waiting for the transfer. I'd recommend walking to the seawall, turn right, check out the Baron Bliss Monument, continue on and you'll see "Tourism Village," keep going and you'll see Sea Sports Dive Shop, keep going and you'll see the Swinging Bridge. Continue over the bridge, walk past the square and check out the Supreme Court Building and the park just past it. Assuming you've come this far, about a 20 minute walk, you might want to continue to the Governor's House on the left and St Johns Cathedral on the right a few more blocks down. Peek in the church. It's very cool. Then walk back the way you came.
If instead you're stuck at the Princess Marina, walk along the seawall to the Baron Bliss Monument, then turn around and go back. You might cut across the street and walk through the somewhat dilapidated neighborhood but don't go into it more than a block or so. There are some cool things to see in there, like the old prison now a museum and the old American Embassy but they're a little hard to find if you don't know your way around.