Kerama Islands Reefs

Why the Kerama Islands sit at the top of Japan's diving list

Most travellers picture Japan as Tokyo neon, Kyoto temples and Hokkaido snow. Far fewer picture a tropical island archipelago with some of the clearest water in the Pacific — but that's exactly what the Kerama Islands are. Sitting about 40 kilometres west of Naha on Okinawa's main island, the Kerama group is a cluster of about 30 small islands and reefs that punches far above its size for diving and snorkelling. Locals call the water Kerama Blue, and once you drop in you understand why: visibility regularly runs past 30 metres, sometimes far further, and the light plays through the shallows in a way that makes even three-metre swims feel cinematic.

The reefs here aren't a single famous site. They're a constellation of dozens — fringing the larger islands of Tokashiki, Zamami and Aka, plus the smaller uninhabited rocks scattered between them. Together they make Kerama one of the few places in Japan where you can do four dives a day in protected, warm, gin-clear water without ever moving more than a 20-minute boat ride from your dive base.

The reef system is now formally protected as part of Kerama Shoto National Park — Japan's 31st and one of its newest. Designation came in 2014, and it pulled the area into a much stricter management regime: anchor points instead of free anchoring, reef-walking restrictions on the more fragile sites, mooring fees that fund coral monitoring, and quotas at the busiest sites in summer. The result is a place that's still genuinely wild, with healthier coral than most of the surrounding South-East Asian dive triangle, and far less crowding than Okinawa's mainland sites get on a summer weekend.

[IMAGE: https://images.unsplash.com/photo-1582967788606-a171c1080cb0?w=1600&q=80&auto=format&fit=crop | Crystal-clear turquoise water of the Kerama Islands — the famous "Kerama Blue" that pulls divers from across Asia]

Getting to the Kerama Islands

The jumping-off point is Naha, the capital of Okinawa. Most international and domestic flights into Okinawa land at Naha Airport, and from there it's a short taxi or monorail ride to Tomari Port (泊港), the small ferry terminal that handles all Kerama-bound traffic. There are two routes: the slow car ferry, which takes about 70 minutes to Tokashiki and 90 minutes to Zamami, and the faster passenger-only Queen Zamami high-speed ferry that does the run in 35–50 minutes depending on the destination. Schedules tighten dramatically in winter and during typhoon season — verify the day before you sail and don't bank on standby seats in summer.

If you're coming as a day-tripper from Naha, the high-speed ferry is the right choice and the boat operators sync their dive trips to its arrival. If you're staying overnight in the islands (which we strongly recommend — see below), the slow ferry is fine and gives you time to settle in. There's no airport on any of the Kerama Islands, no bridge from the mainland, and no realistic alternative to the ferry. That isolation is precisely why the reefs are in the condition they are.

What you'll see underwater at Kerama

The Kerama reef system supports an unusually diverse fish community for its latitude — roughly 350 recorded species — plus a coral cover that runs from massive plate corals on the deeper outer slopes to dense soft-coral gardens on the protected inner walls. It's a soft transition between the sub-tropical communities of southern Japan and the true tropical Indo-Pacific reefs further south, which means you can see species at Kerama you'd otherwise have to travel to either Borneo or the Izu Peninsula to find.

Highlights divers come specifically for include green sea turtles (almost guaranteed on most sites — Kerama has one of the highest turtle densities in Japan), reef sharks (whitetips on the outer drop-offs), occasional manta rays in the deeper channels, mobula schools, lionfish, octopus on the night dives, and from January through March, humpback whales migrating through the Kerama Channel. The whales come close enough that whale-watching boats run from both Tokashiki and Zamami, and divers occasionally hear them singing from underwater — one of the most surreal experiences in Pacific diving.

Coral health here is among the best documented in Okinawa. Bleaching events have hit the inner reefs harder than the deeper outer sites, but recovery has been measurable since the National Park was designated, and recent monitoring has shown rising coral cover at several previously affected sites. Compared with reefs in southern Thailand, the Maldives or much of the Philippines, what you see at Kerama is genuinely encouraging.

The best dive sites in Kerama

Boat operators rotate sites depending on conditions, but a handful of the regulars are worth knowing about by name:

Toma (トマ) — A coral garden between Aka and Geruma islands, mostly 5–18 metres, considered one of the most photogenic shallow sites in the chain. Soft corals, schooling jacks, easy current. Good for first dives of a trip.

Black Rock (黒島) — Off Zamami, deeper site running 18–28 metres along a sloping reef wall. Reef sharks, large pelagics, more current. Intermediate-only.

Sakubaru (佐久原) — On Tokashiki's east side, 8–22 metres, known for its turtle encounters and the volume of macro life in the rubble between the bommies. Photographer favourite.

Aka Island Wall — Vertical drop-off down past 30 metres, with dramatic light shafts in the morning. Big-fish site — eagle rays, mantas in season, occasional whale sharks. Advanced.

Naga-Naga Cave (長崎洞) — Swim-through and chamber dive at the southern tip of Tokashiki. Bioluminescence on the night version. Briefing-heavy — a good guide makes the difference.

You don't need a dive certification to enjoy the area — the same operators run snorkel-only trips on the shallower sites, and the visibility is so good that you can see most of what divers see from the surface.

When to visit

Kerama is divable year-round. The peak season is May through October, when water temperatures sit between 26°C and 29°C and the visibility runs at its annual best. July and August are the busiest — book accommodation and ferries weeks ahead, as the islands fill up with mainland Japanese travellers on summer holiday.

October to April brings cooler water (down to about 21°C in February — a 5mm wetsuit is plenty), some swell, and the bonus of the humpback migration through the Kerama Channel from January to March. The visibility actually improves slightly in the cooler months because of reduced plankton, so winter divers often get the best photo conditions.

Typhoon season (mid-July through October) regularly cancels boat trips, sometimes for several days at a time. If you're flying in for a short trip, build a day's slack into the itinerary so a single weather window doesn't ruin the whole plan.

[IMAGE: https://images.unsplash.com/photo-1583212292454-1fe6229603b7?w=1600&q=80&auto=format&fit=crop | A scuba diver above a healthy reef in Kerama — the protected reef system supports hundreds of species across an unusually small area]

Where to base yourself

You have three realistic choices. Naha (mainland Okinawa) as a day-trip base works for divers on a tight schedule — early ferry out, two dives, late ferry back, dinner in Naha. The downside is two hours of ferry time eating into the diving day.

Zamami Island is the best balance for most travellers. It's the largest of the inhabited Kerama Islands, has the widest choice of guesthouses and dive operators, and a small village with a few decent restaurants and a beach within walking distance of the port. Dive operators here will often pick you up from the ferry, drop you back to your guesthouse between dives and feed you on the boat — the all-inclusive Japanese guesthouse model at its best.

Tokashiki Island is quieter, slightly more developed in its main resort cluster at Aharen Beach, and has the best beach diving on the Kerama chain. If you want a few non-dive days mixed into the trip — paddleboard, hike, snorkel from shore — this is the better choice.

Aka Island is the smallest of the three and the most rural; ferry traffic is lighter and accommodation is mostly minshuku (family-run guesthouses). It's a niche pick for travellers who specifically want quiet and don't mind a more limited dive-operator selection.

A note on accommodation generally: standards across the islands are practical, not luxurious. Expect clean tatami-mat rooms, futon bedding, communal bathrooms in the smaller minshuku, and excellent meals included in the rate. English is limited at most places — bring patience and a translation app. If you want a Western-style hotel, stay in Naha and day-trip out.

Combining Kerama with the rest of Okinawa

Most international travellers won't fly all the way to Okinawa just for Kerama, and you shouldn't either — the wider region pairs naturally with a longer trip. The mainland of Okinawa has its own dive sites (the Blue Cave at Cape Maeda is famous, if crowded), the WWII history sites at Itoman, the food and music of the central towns, and the long sub-tropical drive up the west coast to Cape Hedo. Further south, the Yaeyama Islands (Ishigaki, Iriomote, Taketomi) are a 50-minute flight from Naha and offer another full week of jungle, mangroves and reefs. A 10-day Okinawa trip that opens with three days at Kerama, three days driving the mainland, and four days in the Yaeyamas covers the islands properly.

For practical visitor information about the National Park itself — protected zones, mooring rules, boat licensing — the Ministry of the Environment's Kerama Shoto National Park page is the authoritative source. For ferry schedules and accommodation across the islands, Okinawa Tourism's official site keeps an up-to-date directory of operators and current weather impacts.

Plan your Kerama visit

Already certified and ready to dive? Look at our related tours from Naha and the Kerama Islands — they include shore-based dive packages, multi-day liveaboards, and snorkel-only day trips. If you're using Kerama as the diving anchor for a wider trip, our Japan country guide walks through the regions month by month, and the Japan travel writing index collects all the trip reports, reviews and journals our community has filed from across the country.

Whatever you do, don't make Kerama a side trip. Block out at least three full days, take the slow ferry over, settle into one of the island guesthouses, and dive every morning. Few places in Pacific Japan reward a proper visit the way the Kerama reefs do — and few are still in this kind of condition.