John Oates has just returned from a research trip to the Philippines. While he was there he fell in love with the island of Siquijor, a place of pristine beaches, great diving, and a healthy dollop of black magic mystery.

Tell a Filipino that you plan to visit Siquijor and there is a fair chance that they will warn you to stay well away. If you really must take the short ferry ride from nearby Negros, they say, don't even think about going out at night on an island famously inhabited by mangkukulam (magicians).

Local authorities insist that the only magic practised is used for healing, and on Good Friday each year the magicians do indeed get together to mix up a huge potion. Yet the rumours of black magic continue, and in 2007 the Tagalog film Siquijor: Mystic Island portrayed a TV crew who were cursed after faking an exorcism on the island.

In reality Siquijor feels far from threatening, although watching the film just might lead to an early demise through sheer boredom. The island is actually a perfect place to include in a Philippines itinerary: a manageable size, friendly and with some great but largely undeveloped beaches. It also has ferry connections to Cebu and Bohol, as well as nearby Negros.

Little is known about the island prior to the arrival of the Spanish in 1565, but they seem to have been enchanted by its fireflies and dubbed it the Isla del Fuego (Island of Fire). Today Siquijor attracts a steady trickle of foreign visitors, including the inevitable scuba divers. The highlight of the handful of dives which I took there was to a 60m-long Japanese ship, which was sunk by American forces in 1945.

Back on land, a 72km ring road - unusually well-surfaced for the provincial Philippines - makes for an excellent day trip if you hire a motorcycle, or a motor rickshaw with driver.

Heading clockwise from Sandugan Beach, which has a collection of low-budget resorts, the first stop is likely to be Salagdoong Beach which is frequented by Filipino families who come to eat and sing karaoke. It's also a favourite spot for daredevils to test their mettle by flinging themselves off the rocks into the sea. The karaoke and the watery death wishes may or may not be related.

Further along the coast, the southern port town of Lazi has a coral-built church and provides access to the Cambugahay Falls. The falls are a good place for a cooling dip, as long as you don't mind attracting some attention as a foreigner.

So far, so non-mystical. Indeed, unless you arrive in Holy Week or make specific enquiries you are unlikely to encounter much in the way of witchcraft beyond a couple of resorts offering massage by traditional healers. The nearest you're likely to get to spooky, then, is a stop at a 400-year old balete (ficus) tree close to Lazi. Locals believe that these trees are inhabited by spirits, and looking at its gnarly bark and hair-like tangles of vines you can see where the idea came from.

The road continues through the town of San Juan, where you can swim in a sulphurous lake, and there's a turning for the lovely Paliton Beach. Whatever stops you make, try to be on the west coast as the sun goes down - when I took the trip the vivid orange and golden sunset was the best that I have ever seen. As night fell and the fireflies came out, I had already been bewitched by Siquijor.