I really have no open water experience so this is great advice. The sound is freezing cold these days but I think I have to bite the bullet and buy a wetsuit nowI’m glad you posted this because it was going to be my next question. If you don’t have a lot of open water experience, I would suggest you train on that part most. My experience is most first timers DNF within the first 500m of the swim. Open water is much more challenging than pool swimming. For one, there’s no wall to push off. 200 meters, 300 meters or 400 meters looks a lot farther when you’re just out there in the middle of a lake. Throw in murky water and other people smacking your head or feet, and it can be very unsettling. Let alone 1500 meters.
There’s also the elements to deal with. As already mentioned, it’s going to be cold. The water will be murky and sighting your buoys is going to take some practice. Plus, unless it’s an exceptionally calm day, I can all but guarantee the water will be moving quite a bit more than what you’re accustom to in a pool. I’m noticeably slower in an open water swim than doing laps in a pool. Much of that is just because, in a pool, the water is only so turbulent, so it’s easy to get a good rhythm and minimize breathing. If you’re dealing with waves breaking over you, it’s going to play havoc with your rhythm. You really need to get comfortable swimming open water, and honestly, 90% of that is just mental. Keep calm and remember you can always rest on a kayak or buoy. There are always eyes on you for safety.
I really can’t stress this enough. Prepare yourself mentally and you’ll do fine.