At the break of dawn, a group of swimmers step into a quiet lake, scanning the open horizon. There are no lane lines, no black lines on the bottom of the pool. Simply the water, wind, and the unknown.

To perform well in training for SEALs, Navy EOD, Dive Schools, SWCC, Marine Recon, Air Force PJ, Rescue Swimmer and other special diving programs, you must master swimming straight (and fast). When ...