Why Divers Detour to a Sandbar That Isn't Really an Island

Barasu Island, often written as Barasu Sandspit or "Barasu-jima," is not a permanent landmass at all — it's a mobile accumulation of bleached coral rubble and fine white sand sitting in the shallow channel between Iriomote and Kohama Islands. Tides and typhoons reshape its outline year to year, sometimes shrinking it to a sliver, sometimes building it back into a proper crescent. For divers, this instability is exactly the draw. The surrounding seabed is a rare combination of open sand flats, coral bommies, and current-swept channel edges, all in water shallow enough that light penetrates all the way to the bottom even at 15–18 meters.

This is a spot built for a specific kind of diver: one who loves macro photography and doesn't need a wall or a wreck to be entertained. Sand diving here means slow, deliberate fin kicks a few feet off a pale seafloor, scanning for garden eels swaying out of their burrows, peacock mantis shrimp patrolling their tunnels, juvenile flounders doing their disappearing act, and the occasional blue-spotted stingray gliding past in the open. Because the substrate is sand and rubble rather than hard coral, visibility on the bottom stays exceptionally clean, and the light-colored floor acts almost like a photography studio backdrop — subjects pop in a way they never do against dark reef.

It's not a dramatic, big-animal dive site. If you're chasing mantas or shark encounters, Iriomote has other spots for that. But if you want unhurried macro work, near-guaranteed calm conditions, and a sandbar you can also surface-swim to and stand on between dives — sometimes literally walking on a strip of sand in the middle of the ocean — Barasu delivers an experience that's genuinely different from the fringing reef dives most Yaeyama itineraries default to.

What the Dive Actually Looks Like Underwater

Barasu sits in the relatively protected water between Iriomote, Kohama, and Kayama Islands, so most dives here are shore-boat hybrid trips: a short boat ride from a Kohama or Iriomote pier, followed by a giant-step or backward-roll entry near the sandbar itself. Depths typically run from a very forgiving 3–5 meters over the shallow sand shelf near the spit itself down to 15–20 meters where the channel deepens toward the reef edges. This depth range makes it workable for both newly certified divers building bottom time and experienced photographers who want to linger at a fixed depth for a macro subject.

The bottom composition alternates between broad stretches of rippled white sand, patches of coral rubble colonized by small gobies and blennies, and isolated coral heads that function as mini oases — expect anemones with resident clownfish, cleaner shrimp stations, and schools of small fusiliers using the bommies as shelter. Because there's little vertical relief, buoyancy control matters more here than at a typical wall dive: silting out the sand ruins visibility for the whole group, so a slow, horizontal fin kick (frog kick over flutter kick) is the etiquette norm local guides will ask for.

Current is generally mild to moderate, driven by tidal exchange through the channel rather than open-ocean swell, which is what keeps the site diveable even when conditions on Iriomote's outer reefs turn marginal. That said, spring tides can accelerate flow noticeably between the islands, so dive shops will often schedule the tour around slack tide windows. Surface conditions are usually flat given the sheltering effect of the surrounding islands, making this a comfortable choice for divers who get seasick on longer boat runs to Iriomote's south coast sites.

Because it's a sand and rubble habitat rather than a reef wall, dive guides here lean heavily on muck-diving technique: slow scanning, checking burrow entrances, flipping over the occasional shell or rubble piece (and replacing it exactly as found), and using a fine beam torch even in daylight to pick out camouflaged subjects like flatworms, nudibranchs, and juvenile fish sheltering in the rubble. It rewards patience over distance covered.

When to Go and How to Actually Get There

Water temperatures around Iriomote range from roughly 22°C in the coldest months (January–February) to 29–30°C at the height of summer (July–August), so it's a year-round dive destination in a 3mm-to-5mm wetsuit for most of the year and a rash guard in peak summer. The most stable weather window for Yaeyama diving generally falls in late spring (April–June) and autumn (October–November), avoiding both the June rainy season and the peak typhoon risk of July through September. Typhoons can and do shut down boat operations for days at a time in summer, and because Barasu trips depend on a boat crossing, it's worth building slack into a summer itinerary rather than scheduling it on a single fixed day.

Winter (December–February) brings calmer, clearer conditions in the channel and fewer tourists, though air temperatures can dip enough that a hooded vest is welcome on the boat ride. Visibility on the sand flats tends to be strong nearly year-round precisely because the site is sheltered from ocean swell — it's one of the more weather-resilient dive options in the Yaeyama chain.

Access starts at Naha Airport on the main island of Okinawa, from which it's roughly a 55-minute flight to New Ishigaki Airport (OKA to ISG). From Ishigaki, most divers either book a day trip that includes a ferry connection or base themselves on Iriomote or Kohama for a few nights. High-speed ferries run from Ishigaki Port to Ohara or Uehara ports on Iriomote in about 35–45 minutes, and a separate, shorter ferry connects Ishigaki to Kohama Island in around 25 minutes. Many dive operators running Barasu trips are based out of Kohama or Uehara and will handle the final boat leg to the sandspit directly from their own pier, so check with your shop whether you need to arrange the Ishigaki-to-Iriomote/Kohama ferry yourself or whether it's bundled into the dive package. There is no airport on Iriomote itself, and car rental on the island is mostly useful for reaching trailheads and beaches rather than the dive site, since the actual approach to Barasu is by boat regardless of where you're staying.

Booking, Gear, and Etiquette Before You Splash In

Because Barasu isn't a single fixed mooring but a shifting sandbar, always book through a licensed dive shop based in Kohama, Iriomote, or Ishigaki rather than trying to arrange a private boat — operators track the current sandbar position, tide tables, and channel current in a way that's hard to replicate independently, and conditions genuinely change month to month. Most shops offer it as a half-day, two-tank trip, sometimes paired with a second site along Iriomote's reef for contrast between sand-macro diving and coral-wall scenery.

Bring your own mask and a fine-beam dive light even for daytime dives — a torch is essential for spotting mantis shrimp in burrows, checking rubble crevices, and picking out the subtle color of a well-camouflaged flounder against pale sand. A macro lens or wet-mount diopter is the single best piece of gear to pack if underwater photography is your goal; wide-angle shots of the sandbar itself are better done from the surface or a drone, since underwater visibility, while clean, doesn't offer much in the way of dramatic scenery beyond the sand terrain itself.

Buoyancy discipline is the main etiquette point local guides emphasize: sand suspends far more easily than reef structure and doesn't settle quickly in the mild channel current, so a diver who kicks up silt can blind an entire group's macro session for the rest of the dive. Weight yourself precisely, keep fins up and away from the bottom, and let the guide's hand signals dictate distance from the substrate.

Reef-safe sunscreen is non-negotiable, both for the topside sandbar walk many trips include between dives and for the general marine protections in place across the Yaeyama Islands' coral zones. Rash guards are worth wearing even in warm water for sun protection during the boat ride and any surface time on the sandbar itself, which offers zero shade.

For food and stay, Kohama Island has a small cluster of guesthouses and a few casual eateries near its port, making it a convenient overnight base if you want an early-morning slot before the tide window closes. Iriomote's Uehara area has a wider range of minshuku (family-run guesthouses) and restaurants serving Okinawan and Yaeyama specialties like yaeyama soba and grilled ishigaki beef, which make for a good post-dive reward. Either base works; the deciding factor is usually which dive shop's schedule and pickup point fit your itinerary best.