nets

Huge nets billow like butterfly wings.  

From Wikipedia:

The Chinese fishing nets (Cheena vala) are fixed land installations for an unusual form of fishing — shore operated lift nets.  They are mostly found in the Indian state of Kerala. Huge mechanical contrivances hold out horizontal nets of 20 m or more across. Each structure is at least 10 m high and comprises a cantilever with an outstretched net suspended over the sea and large stones suspended from ropes as counterweights at the other end.  Each installation is operated by a team of up to six fishermen.

The system is sufficiently balanced that the weight of a man walking along the main beam is sufficient to cause the net to descend into the sea. The net is left for a short time, possibly just a few minutes, before it is raised by pulling on ropes. The catch is usually modest: a few fish and crustaceans — these may be sold to passers by within minutes.