Interesting story. That will do it.

We were making the passage from Granada to Trinidad and were near the end. 8:00 AM and 10 miles out. It was an absolutely flat sea and we were motoring. These 2 foot swells started marching toward us from exactly our stern moving at about 30 knots. The swells were moving so fast that the tops were blowing off causing a rainbow effect. As the swells passed the feathering tops made a swooshing sound and you could feel the wind and spray from the speed of the swell.

Those 2 foot swells were close together and perfectly straight from horizon to horizon marching through a calm sea, passing up at 30 knots. Everything else was still. Really weird, and beautiful. Lasted about an hour.