There are two other methods of communication: One is audio, the other is tactile. A
Swimovate watch will vibrate at certain intervals, depending on what it is you want: at certain times, or laps, or a certain distance. This is a powerful device. It will vibrate in an open water swim when at a particular distance (if you want to swim a mile, it'll vibrate at the half-mile, telling you that you've reached the turnaround point).
Then there's audio. You think your earbuds are for music, at least when you're in the water. Nooooo. Let me ask you, who would you like to have coach you for a swim workout? Gary Hall, Sr.? Sheila Taormina? Andy Potts? Jan Frodeno? Daniela Ryf? Well, why not? A company like Kuai could send a script to any of these to be read and recorded with certain key phrases which include technique reminders. The phrases are cut and edited, producing workouts for any speed and leave interval. If it's a set of 100s on the 1:20, 1:30, 1:45, 2 minutes, you just edit the prompts – a bell in your ear for lap, every push off the wall, to tell you whether you're ahead, behind, or on pace – and a count as you enter each 50, 100 and so forth. Sheila's voice says, “5 seconds, 3, 2, 1, go” and it's off for another 100. “Ten down, 2 to go, in 3 seconds, 2, 1, go.”
The entire workout is audio, and you don't even need a pool clock.