Once upon a time when it was my livelihood to remain physically fit, I swam 1 mile for every every two miles I ran. Swimming miles in rivers & lakes was far easier than turning constantly in a pool. Yet the currents and tides of the ocean far outweigh the extra buoyancy of salt water. The intercostal & the Saint Johns are not exactly pristine waterways, yet they offer many of the same maritime critters as the open ocean. Granted any watercraft is preferred, but with our weather is a watercraft always going to be available when needed?