I live on the North East side of DFW, so I haven't swum in Lake Grapevine. I do my OWS in Lake Lewisville, in The Colony. As Lundy noted, PlayTri does supported swims in Lake Lewisville...and I think they are open to the public for a small fee ($10ish). Triple Threat Tough (out of TriShop - Plano) also swims in Lewisville (on Sundays, I think). I don't know if they do non-members, though. The TTT coach is also my swim coach.

Also as noted by Lundy, lake temp will be WARM. Wetsuit would not be recommended or even tolerable. air temp that time of year is still in the 90s and can break 100F (rarely). Even overnight, it probably won't drop below 75F, but high 60s isn't uncommon. September is one of my favorite months here.


Since you are from Canada...have you swum in southern US lakes? They are not clear. You likely won't be able to see your hand on the pull.

Watch out for 'gators.


ETA: Since it will still be recreational boating season, there will lots of bass boat, jetski, and other boating traffic. Bring a swim buoy, and orange cap. There is a protected swim area at Stewart Creek Park, on Lake Lewisville...I've done numerous solo swims there. Looks to be about 25 minutes from where you will be staying up the 121 toll-road.

Incidentally, there is also a nice run trail around the edge of the lake....where I've done swim/run bricks. It makes for a nice Saturday or Sunday morning. My wife often comes, and brings the dog. They hang out while I do my thang, then we have a picnic lunch. I'll be there most weekends in September/October prepping for late season races.