The work of a curious fellow
The barnacles we encounter are Northern Rock Barnacles. They live from the high tide level down to beow a hundred feet. They are sessile, meaning as adults they live attached to solid surfaces. In deep water, here about 30 feet, they reach a size of about 1 inch in diameter. They feed by using their legs to gather plankton and stuff it into their mouths.
Barnacles feeding Barnacles feeding