The Dive Masters at Temple Adventures Diving had everything they needed: tanks, a compressor, and tourists looking to take a dip in the Bay of Bengal. The only thing they lacked was was their own reef, which is precisely what they built over the next five months by bringing trees and assorted architectural elements out into the bay. Five months after they began construction, Temple Reef is awash in shoals of fish.

Located off the coast of the former French colony of Pondicherry, Temple Reef has welcomed around 500 visitors. What they've seen is subtly remarkable. Frogfish camouflaged as rocks crawl across the sandy seafloor, carpets of silver garden eels retract at the first signs of danger, and schools of barracuda eye the finned congregants hungrily. A little more than twenty feet from the six-foot iron dome that serves as the new reef's hearst, angelfish swarm around a barnacle-encrusted scooter.

Temple Adventures Australian director Rob Partridge, got the idea for the reef from local fishermen, who traditionally create reefs by tossing trees into the water. The only problem with that strategy? "They biodegrade very quickly," Partridge saws. So he opted for something a bit more permanent.

The metal tower at the center of Temple Reef, assembled piecemeal underwater, was once a formwork for molding in-ground water storage tanks. Six tons of recycled concrete and rocks weigh down the structure and prevent trawling nets from ripping apart the reef. For now, it appears out of the blue like a ruin, but it's easy to see that it will be entirely obscured by sealife. At some point, everyone will likely forget how it even got there.

But the novelty of the ruins is part of the attraction that draws the few tourists in this corner of India onto a boat at the break of dawn and into the swirling depths. Fishermen watch divers pass from their boats – more bound logs than actual vessels – and return around lunchtime. The journey ends with French cuisine and drinks at Artika, a gallery and outdoor cafe popular with locals curious to hear about the new landscape just off shore.

More information: Two dives cost $73, $10 more if you need equipment. Stay at the Hotel du Parc (Rooms from $60) back in town for a refined, but tropical experience.