sea whistle; diver's whistle
A traditional whistling sound made by ama (海女) divers when they surface and exhale, used as a signal upon returning to shore. The term is culturally specific and may require explanation.
See also: 海女
The ama diver returned to the beach while making the sea whistle.
The sea whistle is one of the traditional signals of ama divers.
Compound of 磯 (iso, 'rocky shore') and 笛 (fue, 'whistle'), referring to the whistling sound made by divers near the shore. The exact historical origin is uncertain, but it is associated with the traditional practices of ama divers.