This storm developed very rapidly off to the west of our position at 11:30AM, Thursday 8/7. What was a clear sunny day soon turned more ominous. There also were two other storms developing to the northwest and north. I was on watch while the others were below deck, I called them up to have a look. The water spouts were small a dissipating quickly and only this storm to the west had visible water spouts. Then the bigger one formed and grew with intensity as I was photographing them. We turn on the boats radar to track the storms position and movement. It was 4 miles west and tracking east, southeast. We were headed south, southeast under motor only and as a precaution I turned the boat to the north briefly. The storm then headed south and weakened and we continued on our proper course to Saugatuck, MI.