The survey of the floating sea weeds from quantitative point of view, such as the distribution and the seasonal change in amount, had been included in the first step of this series of investigation. An attempt to estimate the amount of the floating seaweeds was carried out monthly from May, 1958 to June, 1959 along a straight line between Tsuyazaki of northern Kyushu and Oki-nosima Island. The floating seaweeds seen in the sea surface of about 20 metres wide were rated among the following ranks : 1 kg, 1～10 kg, 10～50 kg, 50～100 kg, etc., and then enumerated separately when the survey ship was running along the course. Estimates for the amount in kilogramme of the floating seaweeds were got as the sum of product of number and assumptive mean weight of each rank. The following results were obtained : 1) Amounts of the floating seaweeds observed along the survey course mentioned above showed a considerable seasonal fluctuation, the month of May finding the largest amount (Fig. 2). 2) In general, the floating seaweeds distributed more abundantly in the coastal water, and were rather scanty in the offshore water. However, no small amount of them appeared in the latter water during the season of their larger growing in abundance (Fig. 3).