Did Casco Bay last year and returning this year. For a wetsuit, I opted to just use my regular, long-sleeve tri wetsuit (B70 Helix) and it worked out fine. The weather started in the low 60s and got close to 90 by the end, so for one of the later runs that was also 3+ miles I opted to unzip and pull the top down. Took some extra time but my teammate and I were in it more for the experience than to have speedy transitions. I did get a swimrun specific suit for this year though. I didn't want to buy one if I was only going to be doing 1 race (plus, with the sport being relatively new it became difficult to find any in stock anyway) but since I'm doing another and there are some reasonably priced options out there, I got one for this year. But any wetsuit will probably be fine. My teammate wore a sleeveless and neither of us cut the legs or anything and running in the wetsuit was no big deal.

The only rules on equipment usually are that anything you start with, you finish with. So you can use paddles, buoys, etc. There was I think 1 team last year that swapped out fins/shoes and carried whatever they weren't using in mesh backpacks. Their transitions were slow but their swims were faster than most. I think it's probably easier to just swim in your shoes though. They do make swimrun specific shoes, but I didn't use those. I used some Zoot racing flats that for me worked perfectly. No issues running in wet shoes, no blisters or anything. My teammate used Pearl Izumi race flats. There aren't any real rules for shoes as far as I can tell and I saw just about every kind of run shoe out there. Some people wore long socks I think more for protection than anything, in case they slipped on rocks or something. I might wear socks this year only because I wound up with poison ivy on my ankles. Pull buoys are a must, really, if you're swimming in your shoes. You can thread a bungee cord through and attach it to your leg so that when you are running you just move it to the outside, and that also keeps it in place while swimming so you don't have to squeeze your legs to make sure you don't lose it. It feels a little odd at first, but it didn't take long before it felt totally normal. I didn't use paddles last year because me without paddles and my teammate with them made us about the same speed. But if you do plan on swimming with paddles make sure to train with them a LOT, because she said in spite of doing plenty of swimming before the race, her shoulders were killing her from the 4-ish miles of swimming with paddles. Casco Bay is a particularly swim-heavy course though, so if you are doing less swimming it might not be a big issue.

It's a lot of fun and aside from the wetsuit change I wouldn't change much about my approach from last year. LOTS of Body Glide since it was a lot of ocean swimming. Also we were surprised how kind of sleepy we were toward the end (took over 5 hours) so definitely more caffeine in the race nutrition for this year. Find a way to keep that accessible as well. Swimrun suits have pockets which is great, last year I had gels in my jersey pockets underneath but of course didn't get to those until later in the race when I peeled down the suit.

It's really fun, very different experience. Looking forward to doing it again.

KISS :-)

You don't really need a wetsuit in Mission Bay that time of year especially if you're using a pull buoy to keep your feet up - the swims are quite short and there's enough running that there's more of a risk of overheating on the run than getting cold in the water (January would be a different story). You can use paddles. You could use fins but that course is a full on sprint the whole way with lots of transitions so there's no way you're going to want to take the time to switch between shoes and fins, or carry either around with you while wearing the other. Wear some light, fast draining shoes, strap a pull buoy to your thigh, get used to using your paddles, and just go for it.