October to April is Raja Ampat’s liveaboard season; the Banda Sea opens only twice, in March–April and September–November. The archipelago is calmest and most reliable through the northern-hemisphere winter months, while the stronger south-easterly stretch around July to September pushes most liveaboards out of the region. Hammerhead sightings in the Banda Sea peak September to November, strongest in October and November — reported odds, not promises.
Eastern Indonesia does not have a simple high and low season; it has monsoon patterns that open and close entire regions. Getting the month right matters more here than almost anywhere else in the diving world, because the wrong month does not make a trip worse — it makes half the itinerary impossible. Here is the year, laid out.
What Does Each Month Look Like?
| Month | Raja Ampat | Banda Sea | Notes |
|---|---|---|---|
| January | Main season, reliable | Closed | Wetter, short heavy bursts; strong diving |
| February | Main season, reliable | Closed | Similar to January |
| March | Main season winding on | Window opens — westerly transition | Crossing season; secondary hammerhead period |
| April | Season tapering | Window open | Last reliable crossing weeks before the change |
| May | Transitional | Closing | Boats begin repositioning west |
| June | Weakening | Closed | South-easterly building |
| July | Unreliable for outer regions | Closed | Peak Komodo season; most liveaboards out of Raja Ampat |
| August | Unreliable for outer regions | Closed | As July |
| September | Improving | Window opens — easterly | Hammerhead season begins |
| October | Season opening | Window open | Strongest reported hammerhead month |
| November | Main season | Window open, closing | Strong hammerhead reports; crossings east |
| December | Main season | Closed | Wetter; archipelago diving reliable |
This is a monsoon-pattern summary for planning, not a forecast. Conditions vary year to year and the final route is always set by the actual weather.
Why Does the Banda Sea Only Open Twice?
Because it sits between two monsoon regimes and it is genuinely open water. The transitions between them — the westerly change in March and April and the easterly period from September to November — produce the conditions in which a crossing is a reasonable undertaking. Outside those windows, operators avoid the sea altogether. This is the single most important seasonal fact in eastern Indonesian cruising, and it is why a crossing cannot be added to an itinerary on request in June.
What About the Hammerheads?
The Banda Sea’s schooling hammerhead reports concentrate in September to November, strongest in October and November, with a secondary period in March and April. We want to be precise about what that claim is: an aggregate of operator observation across seasons, not a scientific dataset, and explicitly not a guarantee. Anyone promising you hammerheads on a specific date is selling something they cannot deliver. What can be said honestly is that if hammerheads are the reason for the trip, October and November are the months to ask about. The full picture, including the volcanoes on the same route, is on the Banda Sea crossing page.
What Does the Season Mean for Price and Availability?
Two things. First, the eastern band applies wherever the ship is in the east — $11,600 per night leisure, $12,400 diving, with a five-night minimum — and it does not fluctuate by month; the published tables on the 2027 rates page are the tables. Second, supply is genuinely tight in the good windows. A five-night minimum on a repositioned ship produces far fewer slots per season than a Komodo calendar does, so the constraint you will meet is availability rather than price.
Which is exactly why the next question is when to book: see how far ahead a 2027 charter needs to be booked.
Frequently Asked Questions
When is the best time for a Raja Ampat liveaboard?
October to April is the archipelago’s main liveaboard season, with the calmest and most reliable conditions. Many operators leave the region during the stronger south-easterly months around July to September, which is when LASHA is working the Komodo band instead.
What are the two Banda Sea windows?
March to April in the westerly transition and September to November in the easterly. Those windows are the only times the Komodo–Raja Ampat crossing is sailed, which is why crossings happen roughly twice a year rather than on demand.
When is hammerhead season in the Banda Sea?
Peak sightings are reported from September to November, strongest in October and November, with a secondary period in March and April. That is an aggregate of operator observation rather than a scientific dataset, and sightings are never guaranteed.
Is it worth going in the rainy months?
Often, yes. Rain in the archipelago tends to arrive in short heavy bursts rather than all-day weather, and the diving through the December to February period is among the season’s best. Bring a dry bag and stop worrying about it.
When should I avoid Raja Ampat?
The stronger south-easterly stretch around July to September, when many liveaboards leave the region entirely. It is not that diving becomes impossible — it is that the crossings and the outer regions become unreliable.
Where is LASHA during 2027?
Broadly: Raja Ampat and the east in the archipelago season, crossing in the shoulder windows, and Komodo through the middle of the year. The published season plan and how positioning affects your quote are on the rates page.
Where These Numbers Come From
Vessel dimensions, tank capacities, cabin counts and safety inventory come from LASHA’s own published specification sheet on the yacht page. Charter figures are the published 2026–2027 rate file on the rates page — the same document the Komodo Luxury charter desk quotes from, reproduced in full rather than hidden behind an enquiry form. Government fees are cited to their regulation or issuing body in the text. Anything that is an operational estimate rather than a published figure is labelled as an estimate where it appears. LASHA begins her maiden public season on 17 August 2026, so there are no guest reviews to quote yet and none are invented here. Monsoon windows and hammerhead seasonality are operator-aggregated observations for planning purposes and are labelled as such; they are not forecasts or guarantees. Figures checked 1 August 2026.
Plan This With the Charter Desk
Give the desk a month and a region and you will be told plainly whether the two are compatible. Every LASHA Phinisi Cruise booking is handled by Komodo Luxury, the vessel’s official marketing and booking partner — an operator working Indonesian waters since 2015 and part of Juara Holding Group. Send your month, guest count and how many of the party dive, and you get a written quotation drawn from the same rate bands published on this site, with every separately billed item listed before anything is paid.