PROBLEM TO BE SOLVED: To provide an underwater installation structure which enables to discharge nutrient compositions for a long term and to make constant amounts of aquatic organisms stably establish.SOLUTION: An underwater installation structure which is installed in underwater aimed at growth of aquatic organisms includes: a base 11 which is installed in underwater； an accommodation part 111 which is set up in the base 11 and accommodates nutrient compositions, which specific gravity is larger than that of surrounding water, at sealed states； an outlet part 113 which is set up in the accommodation part 111 and from which the nutrient compositions are discharged； and a water stream control part 14 which controls water stream which disarranges surfaces of the nutrient compositions or stirs the nutrient compositions. An organism carrier 16 which promotes propagation and establishment of the aquatic organisms may be provided on the surface of the water stream control part or inside the domain of the water stream control part 14.
