WHAT is green, amphibious and full of tourists on the trashy banks of the Tárcoles River? It’s not the crocodiles that live there, downstream of the capital’s raw-sewage disposal plan; they probably aren’t full of tourists. Rather, it’s a six-wheeled military relic imported to haul croc spotters along the river – the Stalwart, made by the British luxury car and armored carrier company, Alvis (now Alvis Vickers Limited).Sheldon Haseltine founded Crocodile Safari, a kind of hybrid sightseeing expedition aboard a mid-20th century flagship of the army supply line. The ride itself nearly upstages the crocodiles.For customs purposes, though, the vehicle is in a nebulous region straddling the categories of “yacht” and “bus” – a distinction that translates, of course, into a lot of bureaucratic lunacy and interminable waits for permits.THE entrepreneur brought the so-called “high-mobility load carrier” to Costa Rica, rescuing it from irrelevance after a short-lived heyday in the British army of the 1960s. Dubbed “the Beast,” it is 31 feet long, 8 feet wide and 12 feet high, and guzzles far-fetched amounts of gas from a tank that, at 100 gallons, should be first on government hit lists when oil prices spike.The croc-curious mount the monster’s formidably long entry staircase in the rear and lumber about the riverbanks and floodplain of this major waterway near the central Pacific coast. Crocs and croc sign litter the river almost as much as the litter. Crocs thrive in the trash, a phenomenon that solicited what would seem an odd comment from President Abel Pacheco this year: that sewage should be treated before it is dumped into the rivers, even though a new wastewater policy would drive off tourists who gather to see the crocodiles that live in the filth. The message was: It’s a steep but necessary price to pay for clean rivers.Until that day, however, the green machine is plying the banks, plowing through six-foot-high grass and coaxing hoots and yeehaws from the uninitiated civilians on board.CROC sign is a dark strip of disturbed sand on the wet bank, or a bone, such as a human femur (just kidding). Haseltine rents use of the 320 acres of land along the river from a family that owns the nearby Eco Cocodrilo restaurant and raises horses. Sometimes the crocs take their toll on the horse herd, he said.Around midday, the crocs lie partially submerged just off the bank. Their backs break the surface in long, ridged lines, hard to distinguish sometimes, especially when they are near twigs and Frito bags or whatever the debris du jour might be. Baby crocs swim in irrigation canals and tributaries that flow through the grassy floodplain, and, according to tour guide and driver Gary Pitts, mother crocs lay their eggs just a few dozen yards from the bank in a swampy patch near the property’s dirt road.HASELTINE opted to classify the Stalwart as a yacht in his struggle with customs. As a bus, it would have been denied entry because of its age. He has floated it – it runs at five knots in the water, propelled by two rear jets – but generally, while the water is high, as it is now in the rainy season, he prefers to keep it on land.That does not exempt it from Port Authority regulations, however. Pitts, the Beast’s driver, is a licensed boat captain who has at his disposal something that is likely unique on the Stalwarts that enthusiasts still take on off-road spins – a paddle. It is a wooden paddle, useful, perhaps, on a dinghy near shore, but an anachronistic tribute to the wisdom of bureaucracy mounted on the inside of the rear doorframe. The paddle, the captain’s license, and the 42 lifejackets hanging from the ceiling of the six-wheeled monster are requirements on any yacht registered in Costa Rica.PITTS takes his role seriously. He dresses in a captain’s uniform, tries to convince Haseltine to pick up one of his own, and wears a pistol. Haseltine, with his unruly hair and eyebrows that look like they could use a trim with a weed-whacker, is much the opposite, seeming like someone who would wear a uniform only if it were part of a prank, and a suit only in his coffin. At 58, he is an indefatigable talker with decades of international and spy experience (the latter by proxy) to draw on for anecdotes. His father was a U.S. Central Intelligence Agency operative based in France, where he was born, and his mother was from England, where he spent part of his childhood. He’s married to a woman from Kenya who lives in England and, he admits, is cold on the crocodile tour idea.If Haseltine tags along on one of his company’s tours, a chat with him alone is almost worth the trouble to get to the river, and if the value does not stack up in conversation quality, he easily compensates in quantity.THE tour leaves regularly from 10 a.m.-4 p.m., Saturdays and Sundays, and lasts 45 minutes to an hour. Tickets cost ¢5,000 ($10.40); accompanied children 13 and younger may ride for free. For more information, visit www.crocodilesafari.com, call Haseltine at 288-0208 or 394-2370, call Pitts at 811-8939, or leave a message with the restaurant Eco Cocodrilo at 661-8261.