I think they use (or used to) Crisco for swimming the English Channel, so I suppose it is the same principle. I went to a swim camp in high school (all those years ago), and the head coach had done that. Seems extreme to me for a sprint tri, especially the slipping & sliding issues on the bike, and the potential sunburn. I did do one once (probably got my wetsuit right after that) where the water was something like 55F - glad it was really short! My husband wore 2 or 3 swim caps, and still couldn't keep his head in the water - swam most of the way like Tarzan.

To me, it sounds chilly, but not horrible. I just converted to F, and 62.6F (17C) to 68F (20C) sounds pretty normal for around here. 70 would be nice, but I think the hardest part would be getting in the water in the first place.

Good luck, and have fun!