Those who dive in Moalboal or elsewhere in the Tañon Strait have no doubt encountered currents ranging dramatically in intensity and direction. While diving along the wall one faces areas of notable up currents and down currents, as well as the prevailing, and at some times very strong, horizontal currents. There are some dive sites (Looc) known for localized dangerous currents flowing into underwater caves during tidal flows. And the Binisaya term “Liloan” means whirlpool, and the town with that name at the southern end of the strait experiences them regularly.
Although there are many factors that create and influence currents, the dominant currents in the Tañon Strait are of tidal origin.
The moon is a major influence on the Earth’s tides, but the sun also generates considerable tidal forces. Solar tides are about half as large as lunar tides and are expressed as a variation of lunar tidal patterns, not as a separate set of tides. When the sun, moon, and Earth are in alignment (at the time of the new or full moon), the solar tide has an additive effect on the lunar tide, creating extra-high high tides, and very low, low tides—both commonly called spring tides. One week later, when the sun and moon are at right angles to each other, the solar tide partially cancels out the lunar tide and produces moderate tides known as neap tides. During each lunar month, two sets of spring tides and two sets of neap tides occur.
Within the Tañon Strait, typically, flood tides move surface currents northward while ebb tides move surface currents southward. During the NE monsoon (“amihan”), surface currents during flood phase show a predominantly strong northward flow at the eastern side (close to the Cebu coast, including the vicinity of Moalboal) of the strait which reverses during ebb tides. During SW monsoon (“habagat”), surface currents in the northern boundary do not seem to undergo complete reversals but show cross strait transport just off the northern tip of Negros Island. Unlike the northern boundary, the flow through the southern boundary undergoes more complete reversals with the tides.
At Pescador Island the current is most often heading northerly, despite the tides. Most dives begin in the shallows at the southern tip of the island and proceed to the reef wall on either the east or the west side. However, occasionally the current reverses and flows strongly in a southerly direction. Moderately strong down currents are common on the southwestern corner of the wall.
