Even though people are already using their Apple watches for swimming, it was always going to be an exclusive to the series 2 because it being (advertised as) water resistant is one of its selling points - surely you're used to this by now, even if the previous model supports it, it isn't available! 😛
I've pre ordered the series 2 but I'd still take neither my original watch or the new one swimming with me, something about taking electronics under water doesn't feel right!