The gorgeous views from the water account for the popularity of cruising here. It's essential to book ahead between mid-December and March. All boats leave from the Milford wharf area. Avoid the midday sailings, as they link with tour buses and are the most crowded. Southern Discoveries and Real Journeys run more than a dozen cruises a day between them, with extra options in summer.

Real Journeys. By far the most satisfying way to experience Milford (or Doubtful) Sound is to do an overnight cruise; it gives you more time in the fjord when it's at its best—first thing in the morning and early evening. Kayaking off the boat gets you right up to that mossy bush and rock face. There are two overnight boats: the Milford Mariner's the more luxurious cruise with roomier bunks (with en suites), but the Milford Wanderer's not too far behind. Fewer passengers and shared facilities make it a very friendly boat. An overnight cruise includes a superb dinner and breakfast. But if you only want to do a day cruise, go for the Nature Cruise over the Scenic Cruise. It's more personal, a bit longer (2½ hours), and it's on a boat with more character and a nature guide you can ask questions. Both trips cruise the full length of Milford Sound to the Tasman Sea and have the same extraordinary views of waterfalls, rain forest, mountains, and wildlife. Lakefront Dr., Te Anau, Southland, 9600. 03/249–6000; 0800/656–501; From NZ$355 per person overnight; NZ$72 for day. Overnight cruises don't operate through winter (mid-May–Sept.).

Southern Discoveries. You can't miss Southern Discoveries' big red boats in Milford Sound. If you're only here for the day the Cruise/Kayak option is great for getting close to the shore and seeing the edges of the fjord in all its lush detail—right down to its damp, green, earthy smell. It's an easy paddle on calm water so no experience is necessary. Kayaking starts at the Discovery Centre and Underwater Observatory, which is also included in the price and is well worth a visit. Milford Sound Wharf, Milford Sound, Southland, 9679. 03/441–1137; From NZ$70.