The short answer: buy the layout you need
Choose a lower-deck cabin when its beds, space and quoted price suit you and you accept the stairs and porthole arrangement. Choose a main- or upper-deck cabin when larger windows or a particular room layout justify the premium. Neither deck label tells you enough about engine noise, access to the dive area or emergency escape.
Start with the current named cabin plan, not a generic upper-deck upgrade. Arenui has both master suites and deluxe twins on the deck its plan calls main deck. Dewi Nusantara’s main-deck Master Suite is a different proposition: one substantially larger room, compared with eight lower-deck staterooms.
Arenui: named cabins and deck planWhat a real deck choice changes
Swipe or scroll sideways to compare every column.
| Your decision | Lower-deck option | Main- or upper-deck option |
|---|---|---|
| Dewi Nusantara example | Eight 20-square-metre Deluxe Staterooms; twin or double; porthole | One 46-square-metre aft Master Suite; king bed; stern-facing windows |
| Arenui example | Four named deluxe cabins; individual bed arrangements differ | Rama/Shinta master doubles and Barong/Ganesh deluxe twins on the named main-deck plan |
| Windows and room category | Check whether the named room has portholes and what light they provide | Check window size and view; do not assume every cabin is a suite |
| Stairs and daily route | Trace cabin-to-dining and cabin-to-dive-deck steps | Trace the same route: main deck and upper deck are not standardised names |
| Noise and motion | Deck alone does not establish quietness or personal comfort | Deck alone does not establish quietness or personal comfort |
| Emergency arrangements | Confirm the cabin’s exit and escape arrangements | Confirm the cabin’s exit and escape arrangements; an upgrade is not a safety certificate |
Dewi Nusantara: a space upgrade, not just a window upgrade
Dewi’s eight lower-deck Deluxe Staterooms are 20 square metres, air-conditioned, en suite and adaptable to twin singles or a double. Each has a porthole. They are the relevant comparison for two friends who need separate beds or a couple weighing the standard category.
The 46-square-metre Master Suite is aft on the main deck, with a king-size bed, sitting area, bath and shower, and a stern-facing 180-degree view. Its main advantage is substantially more living space as well as windows. It is not a like-for-like twin cabin higher up the boat. Compare the actual category quote and bed requirement before choosing it.
Dewi Nusantara: Master Suite and Deluxe StateroomsArenui: the higher cabin is not always larger
Arenui’s Rama and Shinta master suites are 20 square metres with king-size beds. Barong and Ganesh are 19-square-metre main-deck deluxe twins with separate single beds. The lower-deck Legong is described as 21 square metres with a king-size bed. An upgrade therefore does not buy more floor area than every lower-deck room.
The operator’s prose calls the four-cabin level upper deck, while the named plan and room headings call it main deck. Reserve by cabin name and plan position. For friends sharing, Barong or Ganesh can solve the separate-bed requirement without selecting a master double. For a couple prioritising a particular bed and room area, Legong merits a separate quote rather than automatic rejection because it is downstairs.
Arenui: named cabins and deck planNoise: look beside, above and below the room
Arenui places the galley, restaurant and dive deck on the level containing its main-deck cabins, and describes its stern as the working area for tenders and dive equipment. That makes the cabin’s exact position relevant; it does not measure the noise inside a particular room. The lower deck has its own stair route to these shared areas.
Before paying for a quiet room, get the named cabin’s position relative to the engine room, generators, galley, stairs and tender-handling area. Establish whether the itinerary includes overnight cruising. We have not measured cabin sound levels, so neither a porthole cabin nor a windowed suite is labelled the quietest. Likewise, deck position alone cannot guarantee that someone prone to seasickness will be comfortable.
Arenui: named cabins and deck planStairs, beds and sharing matter throughout the dive day
Trace the route from bed to bathroom, dining room and dive briefing, then to the tender boarding point. Ask for stair and doorway details if access is important; a spacious cabin or the words main deck do not establish step-free access. Neither vessel example here is presented as an accessible-cabin certification.
Confirm whether a double converts to true twin beds, whether either berth is a bunk, and whether the booking buys a shared berth or sole use. White Manta’s FAQ, for example, limits its single-occupancy offer by boat and deck: White Manta uses main/lower cabins, while Blue Manta limits upper/main single-occupancy twin cabins and otherwise uses the lower deck. The published 20% supplement is subject to availability. A cabin upgrade and a solo-occupancy supplement answer different questions.
White Manta: fees, Nitrox and occupancy FAQCheck escape arrangements independently of cabin comfort
The UK Marine Accident Investigation Branch’s February 2025 Red Sea dive-boat bulletin identified escape routes through lockable doors, missing markings or lighting, and poor or absent briefings among its accident findings. It advises booking through vendors able to provide assurance about vessel safety standards and requesting a thorough briefing before departure.
That bulletin concerns Red Sea accidents, not an inspection of Arenui or Dewi Nusantara. Its relevance to choosing a room is that windows, deck height and price are not proof of a usable emergency route. Before departure, understand the route from your own cabin, the emergency equipment and muster arrangements. Do not assume a porthole or a large picture window is an emergency exit. No cabin in this comparison receives an independent safety endorsement.
MAIB: Safety Bulletin 1/2025, Red Sea dive boatsWhat to put on the cabin confirmation
The useful confirmation names the vessel, dated departure, cabin name or number, deck-plan position, bed configuration and shared-versus-sole occupancy. It should also identify the supplement and what happens if the operator changes the room or boat. A request for upper deck without those details leaves too much unresolved.
For Arenui, the published Rama/Shinta supplement is USD 50 per person per night, so an 11-night upgrade adds USD 550 per person. Whether that is worthwhile depends on the named room, not the idea that higher is automatically better. Keep that upgrade separate from park fees, Nitrox and flights when comparing the final trip cost.
Arenui: dated schedule, prices and inclusions