Coast Guard Bouy tneder in Grassy Sound Today

There is a Coast Guard Bouy Tender in Grassy Sound today Just north of the RR Tressel and south of the NWW Stakes. I wonder if they are taking measurements for dredging. Although I saw two people in wet suits flippers and masks with ropes tied around their waists jump into the water. One had a deck brush and would submerge and then resurface. Climb aboard and then back into the water. A person was on deck holding onto the rope for each person who went in the water. I have not seen this before back in the Grassy Sound. A training run maybe? The boat was anchored.