Abstract
Very large floating structures of several kilometers long and . wide are now considered as possible alternatives to such land-based big facilities as an airport. Since the principal horizontal dimension is so large that the conventional experimental tanks can not comply with the appropriate similarity law, an attempt is made to carry out experiments in a very small water tank. With the use of a very small tank, the entire wave field around a model or the entire response pattern of the model in waves can be visualized by making use of certain optical techniques, which can not be achieved if the conventional water tanks are used.