Halliburton

The Halliburton is Utila's classroom at depth. Sunk deliberately in 1998, the little freighter stands upright and complete on the sand — mast, wheelhouse, holds — with the tidy proportions of a training diagram, which is how half the island's advanced and wreck students come to know her. Grey angelfish patrol the rails, a moray or two keeps office hours in the machinery, and the anchor line descent through blue haze to a materializing shipwreck delivers the small theater that makes wreck diving addictive. Interior passes are short and prepared, but silt punishes lazy fins.

The moment you come for: Compact upright wreck, textbook deep and wreck training profiles, moody mast-in-the-haze descents.

Topography: A small cargo ship scuttled for divers in 1998, upright on sand at about 30 m with the deck near 20 m.

Entry: Buoyed site a short run from the harbor on the sheltered south side; descend the mooring line to the deck.

Hazards: Depth near the recreational edge and enclosed spaces; penetration needs training and a guide.

Conservation: Utila's principal artificial reef; leave the growth undisturbed for the classes behind you.

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