Abstract: A submersible system is provided for isolating a volume of water located above an underwater substrate and for analyzing the volume of water. The system includes a tent having a shape enclosing an area of underwater substrate and a volume of water immediately above the substrate. A support frame formed by frame members each including plural detachable sections for maintaining the shape of the tent. A securing assembly, comprising a peripheral flap held down by weights in the form of sandbags or a heavy chain serves to secure the tent to the substrate. A circulation system, located at least partially within the tent, provides circulation of the volume of water within the tent so as to maintain a circulating flow pattern within the tent. A flow through analytical system is provided for removing a portion of water from the enclosed volume of water and for analyzing at least one property of the portion of water.