Naha to Zamami, Okinawa: ferry ride rocky?

I have been reading blogs saying the ride from Naha to Zamami can be rocky that people are vomiting for the day. Is this true? When should I go to catch good seas?

Yes, rides with the small ferries between Okinawan islands CAN be extremely rocky, with some people vomiting. I myself felt pretty badly after a recent ride to Iriomote the other day.

But don't worry too much: It simply depends on how high the waves are! Immediately before or after a storm, the waves can be very high and the ferry ride will be beyond imagination with the boat jumping across the sea. On the other hand, when the sea is calm, the ride can be very pleasant.