A monitoring apparatus for an elongate subsea structure, wherein the elongate subsea structure is a riser, the monitoring apparatus comprising: a strain gauge secured to said elongate subsea structure at a defined location, and an information processing means which is configured to receive signals communicated from said strain gauge being indicative of actual strain values experienced by said elongate subsea structure over time, said information processing means being characterized in that it comprises: - a pre-compiled discretised bending moment variation matrix theoretically derived by computationally intensively analysing the response of a virtual model of said elongate subsea structure when subjected to wave-like forces of varying periods and amplitudes for different tensile loadings, - an extrapolation means which utilises the discretised bending moment variation matrix in conjunction with said time-varying actual strain values or processed versions thereof and the known defined location of the apparatus relative to said structure to provide likely actual values for bending moment variation at a plurality of points along the length of said structure, and therefore provide an indication of the likely actual damage being or having been sustained at any of said plurality of points along said structure and remote from said defined location, wherein the information processing means includes a tolerance of slight subsea depth variations in the defined location of the apparatus by utilizing the bending moment variation matrix to create an envelope of possible bending moment variations at a particular point on the elongate subsea structure remote from the site of the monitoring apparatus by retrieving from the discretised bending moment variation matrix the calculated multiple possible values of likely actual bending moment variation occurring at said particular point when the number of known parameters for said particular point is lower than the dimension of said bending moment variation matrix, selecting the maximum bending moment variation value from that envelope of values, and providing this value as the likely actual bending moment variation value for the particular point. - a pre-compiled discretised bending moment variation matrix theoretically derived by computationally intensively analysing the response of a virtual model of said elongate subsea structure when subjected to wave-like forces of varying periods and amplitudes for different tensile loadings, - an extrapolation means which utilises the discretised bending moment variation matrix in conjunction with said time-varying actual strain values or processed versions thereof and the known defined location of the apparatus relative to said structure to provide likely actual values for bending moment variation at a plurality of points along the length of said structure, and therefore provide an indication of the likely actual damage being or having been sustained at any of said plurality of points along said structure and remote from said defined location, wherein the information processing means includes a tolerance of slight subsea depth variations in the defined location of the apparatus by utilizing the bending moment variation matrix to create an envelope of possible bending moment variations at a particular point on the elongate subsea structure remote from the site of the monitoring apparatus by retrieving from the discretised bending moment variation matrix the calculated multiple possible values of likely actual bending moment variation occurring at said particular point when the number of known parameters for said particular point is lower than the dimension of said bending moment variation matrix, selecting the maximum bending moment variation value from that envelope of values, and providing this value as the likely actual bending moment variation value for the particular point. <EOS>