The only time I heard anything at all was in South Carolina when I was anchored in a quiet cove just off the ICW. About 2 a.m. I heard a clicking sound. I grabbed the flashlight and gun, opened the cabin door to find nothing at all. Went back to bed, and a few minutes later, I heard it again, this time I climbed into the cockpit, shined the light around and saw nothing, that is nothing until I shined the light in the water and hundreds of pink eyes were staring back at me. I grabbed the cast net, made one toss and netted about 50 huge shrimp. I suspect they were eating the algae off the hull, which accounted for the clicking sound. Sure were tasty for the next three meals, though.
All the best,