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The Author has had access to a number of model tests data sets for models run at an extensive range of trim and draughts. It has been found that the power versus trim, draught and speed can be represented by the sum of three functions, one dependant on the overall loading condition of the vessel and the other two are dependent on the draught at the bow and the stern respectively. These functions and the bow and stern profiles are seen to be geometrically related. The effect of the profiles on vessel power is clearly shown and it can be seen that there are draughts relative to the local profile at which the power is reduced and others at which the power is increased. This gives valuable insight into the effect of the bow and stern profile shape on power and can be used to help optimise new vessel designs for one or more design conditions. It also gives a way forward to calculate the optimum trim for existing and new vessels based on the limited information typically available to a ship owner/in-service monitoring service, namely; speed trial data, the vessel general arrangement drawing and the scantling drawings.