NOVELTY - The underwater power generating installation structure has a power generating system which is connected with the infrastructure equipment such as electrical transformer equipment. A support structure (6) of infrastructure arrangement (5) is engaged with a bed (3) of body of water. The infrastructure module (7) is releasably engaged with the support structure, so as to house the infrastructure equipment.    USE - Underwater power generating installation structure with infrastructure arrangement for housing infrastructure equipment such as monitoring equipment, electrical switching equipment, control equipment of wind turbine, hydraulic equipment, and electrical transformer equipment (all claimed) used in tidal turbine farm and offshore wind farm.    ADVANTAGE - The same deployment technique can be utilized for power generating units and infrastructure equipment modules, so that the deployment process and retrieval process of infrastructure module can be simplified. The support connection carrier can be removed from the support housing for maintenance purposes, without the need to remove the whole support structure and support housing, or to perform complex underwater cutting and welding operations. The polar mounting freedom of the infrastructure module enables the positioning and orientation processes of the support structure to be simplified. The construction and deployment processes of underwater infrastructure equipment can be simplified. The capital cost of infrastructure equipment can be reduced. The inspection, servicing and maintenance of the infrastructure equipment can be performed in a relatively cost effective and efficient manner.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) infrastructure arrangement for use in an underwater power generation installation structure; and    (2) underwater structure.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the infrastructure arrangement.    Bed of body of water (3)    Infrastructure arrangement (5)    Support structure (6)    Infrastructure module (7)