These circular structures hold deep nets in which fish are raised for commercial sales. There are three groups of these pens off the coast, a bit north of town. The seagulls are in heaven!
This is the boat that pulls up the nets to harvest the fish. Two guys were hard at work, basically in the water with the net. When I took this shot, one of them was up on the deck yelling angrily at a motor boat that had gone by very fast, creating a lot of waves all the way around the enclosure.