Niue sits alone in the South Pacific — a raised limestone island with no river runoff, no silt, and consequently some of the most extraordinary underwater visibility I've encountered anywhere. On a good day you're looking at 50 to 60 metres of blue water in every direction, which is both exhilarating and slightly humbling when you realise there's nothing between you and the deep.
Most diving here runs from 5 to 30 metres, with the reef wall dropping steeply into open water. Entry is almost exclusively by day boat — there are no liveaboards operating out of Niue, and the island has just one or two small dive operators, so you'll want to book ahead and accept that conditions dictate the schedule.
Currents are generally mild, though surge can make shallower sections tricky after weather. The reef structure itself is healthy by Pacific standards — hard coral coverage is reasonable, bleaching pressure exists but hasn't devastated the site the way it has in more trafficked regions, and the absence of large-scale tourism works in its favour.
What you'll actually see: banded sea kraits are everywhere, threading through coral heads with complete indifference to divers, which delights most people and unnerves a few. Nudibranchs are abundant and often spectacular.
Spinner dolphins appear regularly, and between July and October humpback whales use the surrounding waters to calve — you can genuinely snorkel alongside them here, which is as extraordinary as it sounds and is managed with reasonable care by local operators.
Snorkelling is genuinely accessible from several shore entries around the island's coves.
Best visited July to October for whale encounters; open water certification is sufficient for most sites, though confident buoyancy makes the wall dives considerably more rewarding.