An energy generating system includes a dam in an estuary defining a water containment area. The dam includes a plurality of dam elements, each including a plurality of dam panels hingedly connected in series, which are urgeable from an inoperative folded state in a chamber to an operative state by a corresponding pair of main or secondary buoyancy tanks as the tide rises and falls. Each pair of main buoyancy tanks with the corresponding dam element defines a water race within which a water wheel is located. The water wheels are mounted on corresponding drive shafts which are connected in series and which are rotatably carried on support frameworks which are supported on the main buoyancy tanks. Electricity generators are supported on carrier frameworks which are supported on the secondary buoyancy tanks at respective ends of the dam, and are driven by the adjacent one of the drive shafts.