The Karimunjawa archipelago shelters 27 islands inside a 110,000-hectare marine national park, gazetted in 1986 to protect coral formations that rank among Java's most biodiverse. Five islands support permanent settlements; the rest remain forested atolls ringed by white sand and reef flats that drop into channels 40 metres deep. The park's designation followed decades of commercial fishing pressure, and today its waters host over 240 coral species and 133 genera of reef fish, from schools of fusiliers to solitary Napoleon wrasse patrolling the drop-offs. Paket snorkeling Karimunjawa typically launch from Karimunjawa Island's main harbour, where wooden phinisi and fibreglass speedboats queue at dawn. Most itineraries target four or five sites: Menjangan Kecil's shallow gardens, Cemara Besar's seagrass meadows where juvenile blacktip sharks rest, Tengah Island's swim-through channels, and the submerged wreck off Cemara Kecil that serves as an artificial reef. Water clarity averages 15 to 25 metres during the April-to-October dry season, when southeast trade winds calm and plankton blooms recede. The marine park charges a conservation fee of 150,000 IDR per foreign visitor per day, collected at entry points and valid across all zones. Snorkeling tours in the Karimunjawa marine park operate from 08:00 to 16:00 daily, timed to outgoing tides that flush cooler oceanic water into the lagoons. Multi-day packages include overnight stays on Karimunjawa or Kemujan islands, where guesthouses cluster near the jetties. Single-day itineraries return to Jepara by late afternoon, covering five to six snorkel stops in eight hours. Operators supply masks, fins, and rash guards; underwater cameras and wetsuits cost extra. The park authority restricts group sizes to 15 snorkelers per guide and prohibits touching coral or feeding fish, rules enforced by rangers stationed on patrol boats. September water temperatures hover near 28°C, warm enough for extended immersion without thermal protection. Packages typically bundle boat transport, snorkel gear, lunch on a sandbar, and park entry. Island-hopping tours add beach stops on uninhabited cays and mangrove kayaking through Kemujan's tidal creeks. Four-day itineraries include sunrise snorkels, night dives for bioluminescent plankton, and village walks through Karimunjawa town's teak-shaded lanes. Prices reflect boat type, group size, and overnight inclusions, but all routes traverse the same protected reefs.