This text introduces the ‘Detailed scientific and technical report’ of the MAST III project MAS03- CT97-0116 ‘The optimisation of crest level design of sloping coastal structures through prototype monitoring and modelling’ (acronym: OPTICREST). This report gives an account of the detailed scientific and technical outcome of the project referring to the whole project period 1/3/’98- 28/2/’01. For each task or subtask as described in the Technical Annex, this report describes the work carried out and summarises the most important results and conclusions. More detailed information on the scientific results and a description of the methodologies are provided in the annexes enclosed with this report. For tasks which have been finished before T0+12, reference has been made to the final reports on these tasks attached to the first annual report: ‘Annual Report (12 months)’ (ref. no. MAS03/797) and for tasks which have been finished between T0+12 and T0+24, reference has been made to the final reports on these tasks attached to the second annual report: ‘Annual Report (T0+12 till T0+24)’ (ref. no. MAS03/999).