I WIPE THE BUBBLES FROM the front of my camera, and check my depth for the umpteenth time. Exactly 16m. Perfect, just where I was told to be.
The gently shelving coral garden gives way to a sheer wall, and the turquoise water deepens to navy, then black, more than 50m below.
The current wafts me gently along a reef crammed with the very best that tropical diving has to offer.
Im at Pescador Island, described in the guides as one of the top dive spots in the Philippines. Orange, purple and yellow fan corals reach out into the tide along with the green and black spirals of wire coral. Luminous pink soft corals erupt from every ledge, and patches of rock in-between are smothered with sponges, coral and sea squirts in all the colours of the rainbow.
You might imagine that such fabulous scenery would have me clicking away furiously but no, Im on a mission, and it doesnt involve coral.
Fish in every conceivable shape and colour shimmer around the reef. Iridescent damsels flicker among the coral branches and bigeyes lurk beneath overhangs. Lionfish float by with fins and frilly bits outstretched, and fabulously decorated angels and butterflyfish weave through the reef.
Orange and white clownfish keep house in their big fat purple anemones, and boxfish peer squarely from gaps in the coral. But Im not interested in these painted beauties, gorgeous as they are.
My sights are set on a far less flamboyant target and, for fear of wasting batteries, I havent even switched on my flashgun yet.
A turtle drifts down towards me, silhouetted perfectly against the sunburst. My shutter-finger twitches, and my resolve nearly weakens, but the turtle wafts by unrecorded.
The animal Im looking for lives among the grey, leathery tubes of vase sponges, and now Im reaching the section of reef where these bizarre growths are protruding rather rudely from the wall. I zigzag between them, scrutinising each cluster for the superbly camouflaged creature Ive travelled thousands of miles to see.

TIME AND AGAIN IM DISAPPOINTED, and images of long check-in queues, airline food and the dent in my bank account pass before my eyes uncalled for. I spot a likely-looking collection of sponges beneath me and drop down. Nothing there either.
I think of how I lugged my camera gear halfway round the world, and the frustrating week of diving here without it, while the combined expertise of the dive centre and my long-suffering buddy worked out how to repair the flashgun damaged en route.
By this time, Ive dropped to more than 20m, and peer miserably up the wall. The dive guide said they were definitely here. A few metres above, a group of vase sponges sprouts from the reef, gently backlit by diffused tropical sunlight. Bridging a couple of the tubes is a lumpy grey shape, much the colour and texture of the sponge.
My pulse quickens and I reach for the camera, flicking on the flash and rejoicing in the gentle whine as it charges up. I swim up to my holy grail.
There are no fancy patterns or ornate fins, no shiny teeth or intriguing behaviour, but Im in heaven. Ive found my first frogfish, and turn somersaults in celebration. I point it out to my buddy, who appears to be in remarkably firm control of his excitement.
I gaze reverently into the tiny pink eyes and wonder at the jowly, downturned mouth. I photograph my star from all directions, and the frogfish doesnt move a flabby muscle.
Its pectoral and pelvic fins, for all the world like little webbed hands, stay motionless, and its fleshy fishing lure remains stowed against its warty head.
Famed for its ability to eat creatures almost as large as itself, the frogfish relies on the lightning speed of its jaw movement to gulp down animals attracted to its twitching bait.
But this one isnt fishing; in fact it isnt even moving. I look closer, worried that my beautiful fish may be dead - an understandable mistake, considering its somewhat bloated appearance.
Eventually I notice a flap behind each elbow flicker open and close - the fishs gills. I take yet more photographs, and wonder why I find such a bizarre and, some might say, rather ugly fish, so appealing.

YET EVERY DIVER YOU ASK has a favourite creature, and its not always the cute ones. Every day at the dive centre, someone would sing the praises of some curious piece of marine life or another.
One was thrilled by a ghost pipefish, and for another his whole trip was made worthwhile by a dusk dive watching mandarinfish flirt and mate. The smaller the critter, the greater the fascination - this I realised while watching others go to any depths in search of pygmy seahorses on fan corals.
My favourite find so far had been a glorious red-and-white-striped sea cucumber festooned with horns and spikes on a patch of rubble. It wouldnt have looked out of place in a scene from Star Wars, yet my buddy, instructed to pose by this fabulous creature, failed to look impressed.
Some underwater obsessions are more universal. Clown- or anemonefish are always popular, even more so since Nemo hit the silver screen. Dolphins and turtles are on most hit-lists, and earlier that day I had watched in amazement as a boat-load of divers took it in turn to flash frantically beneath a table coral at a group of baby whitetips smaller than my local dogfish.
The whale shark that swept past the whole group one day was undeniably stunning, but still didnt rate up there with my frogfish fetish.
Every few days a seahorse would be found in the shallows by the dive centre, and the place would empty in a stampede for masks and snorkels. Black and covered with rather unpleasant looking fuzzy stuff, the seahorse did the usual manoeuvre of its kind and turned away from every camera.
All the same, food was left uneaten, beers went warm and logbooks were abandoned, even though there were many, far more colourful, camera-friendly pipefish on the reef. Arent they, after all, just unrolled seahorses
It;s not just tropical waters that trigger these strange fixations. Our British seas are fabulous hunting grounds for those who go nuts over nudibranchs, or are potty about tompot blennies.
I was once kissed by a marine biologist 30m down on my favourite reef at home in Sark, after showing him a wall of sunset cup corals.
Apparently he had been looking for them for all his diving life.
Back in the warm water of the Philippines I consider the frogfish, motionless and oblivious to my adoration. Is it perhaps the challenge of finding a creature so well camouflaged, or the fascination of a fish that looks so unfishlike
Could this be a perverse attraction to the plain and lumpy, in a realm in which exquisite beauty is the norm
Whatever the reason, its made my long journey more than worthwhile.

I reluctantly take my leave of the frogfish, but go on to worship two more before the end of the dive.
I photograph both of these specimens from every possible angle.
Back at the dive centre, I proudly display my portfolio of blobby grey fish on a spongy grey background.
My fellow-divers eyes glaze over as I enthuse about my best dive ever, and one is rude enough to say that my beautiful frogfish has the face of a politician. Heathen!
At the end of the holiday, I ask my buddy which of the fabulous marine life wed seen was his favourite. The whale shark, or turtles perhaps
Without hesitation, he declares his love for - batfish.
Batfish, I ask you!
For me, Ive discovered that there are more than 40 species of frogfish worldwide, including those with intriguing words such as hairy and warty in their titles.
Then theres the added challenge of seeing one feed, or even just move.
I think this could be the start of a very expensive obsession.

Magic island for frog-hunters
The Philippines is an archipelago of more than 7000 islands in the heart of south-east Asias Coral Triangle, the worlds most biologically diverse underwater eco-system.
Its a year-round destination with water temperatures of 26-29°C, and visibility up to 30m. Sue Daly dived with Magic Island Dive Resort at Moalboal on the west coast of Cebu Island (www.magicisland.nl).
Magic Island offers excellent-value full-board deals with superb food, the longest cocktail menu Ive ever seen and dive-all-you-can packages, says Sue.
It runs two purpose-built dive-boats which visit sites along the coast and nearby Pescador Island. Most importantly, the team at Magic Island are exceptionally tolerant of underwater photographers, and those with bizarre tastes in marine life, says Sue.