Okinawa seaside and beaches are open for swimming and other sea activities from april onwards. However the temperature of the waters in the sea is about 21 degree Celsius in the beginning of april and about 23 degree Celsius in the later part of april. Hence if you might feel a bit cold if you are swimming. The best time for swimming is between july and october period.
The waters in Okinawa in winter season is cold. It could range from 13 degree or below. Moreover, most beaches might not open during the winter season, so just take note. However, it also means lesser crowd if you want to swim or dive. If you want to swim in winter, perhaps you might want to consider using the pool in the hotel. If not, you can consider wearing a diving suit so you wont feel all cold. Check out these cool Islamic Swim suits. We think it will serve as a really nice looking swim suit for winter too. Bikinis will be for the brave lot and we strongly don’t recommend that swimming in the winter.