Mercer Island police arrested 66 boaters for operating their boats under the influence of alcohol (BUI) over Seafair weekend. The number of arrests was down from last year, when 71 BUI arrests were made.

Police set up a holding pen and base of operations at Proctor Landing.

“We thought that the weekend went very successfully with the high temperatures that we were expecting,” Mercer Island Police Commander Leslie Burns said, adding that the police expected larger crowds and lots of arrests — which turned out not to be true.

Police encountered many designated drivers on boats.

“The crowds were rather small, and our arrests were down,” Burns said.