For bivalves under sand (surf clam (Pseudocardium sybillae), sunray surf clam (Mactra chinensis carneopicta pilsbry) and great northern tellin (Peronidia venulosa)) and the bivalve on sand (scallop (Patinopecten yessoensins)), form factors (e. g., projective area and volume), drag coefficient, lift coefficient and added mass coefficient were measured. Exposed bivalves that are commonly found under sandare most hydrodynamically stable when horizontal currents flow at a 45 degrees angle determined. For the scallop, based on the balance condition of the rolling moment if the main force is lift force and the top is the trailing edge, the critical flow conditions of the habitat can be determined.