Neap tides are those tides which exhibit relatively small amounts of variation and result when the sun and moon are at right angles to each other and therefore tend to counteract each other's effect on the ocean. Spring tides, on the other hand, show the greatest tidal variation (high, high tides and low, low tides) and result when the sun and moon are in alignment with each other, in which case the effect of the two bodies becomes additive.
Okinawa* exhibits what oceanographers consider to be semi-diurnal tides, meaning there are two high tides and two low tides per lunar day. During the year 2018, Okinawa will experience a single low spring tide, on the 3rd of January (01:47am) having a value of -33cm. The highest spring tide will occur on the 12th of August (07:17am), with a value of 238cm. Combined, these minimum and maximum levels result in a value of 272cm (8.9ft) of total tidal variation for the current year.
I've also added Okinawan tidal information from several previous years.
*Tide data taken from WWW Tide and Current Predictor for Naha, Okinawa.