Coral reef and carbonate beach attract many tourists for instance, nearly six million people in Okinawa. However, drowning accidents by a strong offshore current happen every year. Therefore, this paper deals with the physical characteristics of a reef current during winter season at Yoshiwara beach, Ishigakijima, Okinawa Prefecture, Japan, where drowning accidents were occurred by strong reef current during marine leisure activities. Field study on reef current was conducted in November and December, 2006 when northern wind prevailed the study area. The field study shows that the maximum 20-min average offshore velocity could be order of 2 m/s especially during winter season, because the northern wind that is perpendicular to the coast is persistent and generates reasonably high waves
