Biomass production by phytoplankton, whish depends on the nutrient concentration, is regarded as the principal source of the organic pollution in eutrophic bays.
　The A.G.P. (Algal Growth Potential ) test is examined in this ingestigation to deal with the problems of assessment of eutrophication in estuarine and marine coastal situations. A green alga, formulated for the states according to β which is defined as the tangential angle of undisturbed wave profile to the horizontal deck.
　The method is applicable to any value of β, even if it is negative value. The negative β is defined for the state where an air layer is enclosed geometrically by the undisturbed wave profile and structure. This state is occasionally realized for a platform bounded on the shore end by a vertical wall.
　The calculated peak values of total uplift force on a deck give the upper limit of experimental values, although the measured local peak pressures are widely sc
attered. The wave profile is to be estimated with a finite amplitude wave theory. In the present study, the third order approximation theories are apllied to the both of progressive waves and standing waves.