I am a long-time OW swimmer. I do most of my training in a 25 yd pool with once weekly OW swims (mostly spring, summer and fall). I'm gradually getting away from wetsuits. I would like to enter 5K & 10K swims this coming season and want to train accordingly. Mostly, I just do straight laps (typically 1.5 miles/4-5 times per week); there is no interval training. I'm fairly competitive for my age but I just feel that I'm stuck in my workout routine. I need to be convinced that introducing some high intensity interval training - if that's what is called for - will get me to the next level. Any thoughts and experience? Any authoritative reading? I really want my workouts to count!