 It later sold up to 100million admissions including re-runs, the highest for a Soviet film up until "The Red Snowball Tree" (1974).The story is set in a seaside port in Argentina (but filmed in Baku, Azerbaijan SSR), largely among a community of pearl fishers.The protagonist is the adopted son of a doctor/scientist who was sometime in the past forced to save the boy's life by implanting him with shark gills.