Call the CLA and have them investigate and also your town's inland/wetlands commission. No one has authorization to disturb the exposed bottom of the lake. That is private property as mentioned above by Encon.
A few years back a yuppie over in Sail Harbor thought it would be a good idea to dredge out a cove that his property bordered to put in a better boat dock. He got a cease & desist order and had to restore the bottom to its original shape and depth.