5K open water newbie

This September I will be swimming my first 5K open water swim (just throwing myself into this). Does anyone have a training program for a 5K? I am a hardcore runner and have done marathons and half ironmans (open water 1.2 swims). As a runner I crave day-to-day specific training plans. I consider myself a good swimmer (thinking on trying for a 1:20 - 1:25 5K) and/or an intermediate. The swim is Big Shoulders in Chicago, so if anyone is training at Oak Street Beach let me know!!!