Waikiki Rough Water Swim

After about 8 years of not doing any open water swims, I found out that I'm going to be on Oahu (housesitting, no less) at the time of the Waikiki swim (2.4 miles) , so I'd like to take part. I did a 1 1/2 mile swim over the weekend and found myself drifting first to one side then the other. In other words, I probably swam an extra 1/2 mile that I didn't need to. I swim with a Master's swim team, competed at Nationals in Tempe so I'm in relatively good shape -- for pool swimming. But I've forgotten everything I ever learned about open water swimming. Any suggestions about training, technique or the Waikiki swim would be helpful....thanks in advance.