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 2007, Okinawa will experience the lowest spring tide on 27 December with a value of -27cm (01:46am). The highest spring tide will occur on the 27th of September (07:08am), having a value of 227cm. Combined, these minimum and maximum levels result in a value of 255cm (8.4ft) of total tidal variation for the current year.