Hatta Reef

Off Pulau Hatta, the easternmost of the Bandas, a submerged reef runs out from the island and falls away in walls that read as the textbook version of healthy: hard coral to the crest, fans below, and fish biomass that keeps the water column busy from surface to limit. Bumphead parrotfish graze in squads, Napoleon wrasse and turtles work the wall, and schooling snapper and fusiliers stack off the points. This is also one of the crossing's watchlist sites for bigger visitors, with mobula rays and, in the season, scalloped hammerheads appearing out of the blue often enough to keep every diver glancing seaward. Between glances, the wall itself is quietly one of the best in Maluku.

The moment you come for: Steep walls with heavyweight fish life; bumphead squads; realistic odds of hammerheads in season.

Topography: Walls and a submerged reef extension off Hatta island, dropping steeply into very deep water.

Current: The reef's points catch the open-sea flow; drifts along the wall are standard and can accelerate off the corners.

Hazards: Open-sea exposure, current at the points, and blue-water distraction; watch depth while watching the blue.

Nitrox: Worth it here — profiles sit in the range where enriched air meaningfully extends no-stop time (with the training to use it).