A glass-bottom or snorkel day boat for the Gili trade is one of the most commercially direct builds a Lombok yard can deliver: a stable, shallow-draft hull of roughly 10–14 m, a certified passenger deck for 15–30 guests, easy water access for snorkellers, and — for the glass-bottom variant — a watertight viewing well engineered into the hull floor. Build budgets typically land in the range of USD 60,000–180,000 depending on length, material and finish, with the viewing structure itself a modest share of the total. The hard engineering is not the glass; it is keeping the hull stiff and watertight around a hole you have deliberately cut in it.
The mission defines the boat
Gili snorkel operations run short cycles in mostly protected water: morning pickups at Bangsal or the island jetties, two to four reef stops, lunch, return. That profile rewards a specific set of choices — beam and form stability over speed, big shaded deck area, wide side decks and boarding gates, ladders both sides, and engines that tolerate all-day idling between stops. It punishes the choices that look good in photographs: excessive horsepower, deep-V hulls that roll at anchor, and varnished trim that dies in twelve months of sun and salt. Operating economics for this class — load factors, fuel per cycle, break-even seats — are worked through in Gili tourist boat economics.
Engineering the viewing well properly
A glass-bottom section is a trunk: a raised, framed box built up from the hull bottom to above the waterline, with the viewing panels set into its floor. Done correctly, the hull’s structural continuity flows around the opening — doubled frames at each end, carlins along the sides, and the trunk sides tied into the framing so the hull does not hinge at its weakest point. Done casually, the opening becomes a crack-starter and a leak path the operator chases forever.
- Panel material: thick laminated safety glass or cast acrylic, sized with generous margins and bedded in flexible marine sealant — never rigidly clamped, because hulls work at sea.
- Replaceability: panels mounted from inside on bolted, gasketed frames, so a scratched or crazed panel is an afternoon’s job, not a haul-out.
- Protection: external hardwood or metal grounding strips around the aperture, because reef anchorages and shallow sand are exactly where these boats live.
- Drainage and access: the well area sealed from the bilge, with its own drainage, so spilled seawater and cleaning water leave the boat instead of finding the frames.
On desk-supervised builds the trunk framing is inspected before planking or lamination closes it, the same hold-point discipline applied to every structural stage of a custom boat build.
Snorkel-first layouts: water access is the product
For pure snorkel boats, skip the glass and spend the money on access. The features guests actually feel: a full-width stern platform close to the water, twin wide ladders with real treads (not tube rungs), handholds at water level for nervous swimmers, freshwater rinse, shaded gear racks that drain, and deck space organised so thirty wet people can move without bottlenecks. A boat that gets guests into and out of the water gracefully earns its reviews; a boat with a beautiful cabin and one narrow ladder does not.
Stability under crowding is the safety-critical design case. Snorkel stops put most passengers on one side rail at once; the specification must state that loading condition and the hull must pass it with margin. This is where beam, freeboard and deck-height decisions are made honestly — numbers the desk fixes at specification stage, not after the first alarming afternoon in service.
Timber or fibreglass for this class
Both work, and Lombok yards build both well. A timber hull suits operators who value beach-repairable simplicity and traditional looks; fibreglass suits fleets standardising on low-maintenance hulls with moulded viewing trunks. For twin-hull stability at anchor — genuinely attractive for snorkel operations — a small catamaran platform is worth pricing against the monohull, with the trade-offs covered in building a small power catamaran in Lombok. The full material decision framework sits on the hull materials page.
Certification: passenger boats are passenger boats
A snorkel boat selling seats is a passenger vessel in the eyes of the harbourmaster, whatever its size. That means measurement, registration appropriate to its tonnage, safety equipment scaled to its certified count, and crew documentation. Small hulls under 7 GT ride the simpler Pas Kecil route; larger ones carry more paperwork and, at passenger-vessel thresholds, class involvement. Build the certified passenger count into the design brief from day one — retro-certifying an overloaded deck is the expensive way around.
What it costs and how the budget splits
| Configuration | Typical LOA | Indicative band (USD) |
|---|---|---|
| Timber snorkel day boat, outboard pair | 10–12 m | 60,000–110,000 |
| Timber/FRP glass-bottom boat, certified deck | 12–14 m | 90,000–160,000 |
| FRP snorkel/tour boat, higher finish | 12–14 m | 120,000–180,000 |
Engines, certified safety fit and the viewing structure are the main movers inside those bands. Current per-metre bands across all build types, and what shifts a quote inside its band, are maintained on the price and quote page.
Commissioning one of these is a compact project by yard standards — typically two to three dry-season quarters from contract to certified handover. Brief the desk with your route, guest count and stops per day, and the boat that falls out of that brief will be the one your operation actually needs.
Frequently Asked Questions
How much does a glass-bottom boat cost to build in Lombok?
Indicative bands: a 10–12 m timber snorkel day boat runs about USD 60,000–110,000; a 12–14 m certified glass-bottom boat about USD 90,000–160,000; a higher-finish FRP tour boat USD 120,000–180,000. Engines, the certified safety fit and the viewing structure are the main movers inside those bands.
How is the glass viewing panel kept safe and watertight?
The viewing well is built as a structural trunk with doubled frames and carlins, panels of thick laminated glass or cast acrylic bedded in flexible sealant on bolted gasketed frames, external grounding strips for reef anchorages, and sealed drainage so the well cannot flood the bilge.
What matters more on a snorkel boat than speed?
Water access and at-anchor stability. Wide stern platforms, twin real-tread ladders, water-level handholds, shaded gear racks and deck flow for thirty wet guests earn the reviews. The safety-critical design case is most passengers crowding one rail at a snorkel stop — the hull must pass that loading with margin.
Does a small snorkel boat need passenger certification?
Yes. A boat selling seats is a passenger vessel to the harbourmaster regardless of size: measurement, registration for its tonnage, safety equipment scaled to the certified count and documented crew. Hulls under 7 GT use the simpler Pas Kecil route; larger hulls carry more paperwork.
Related reading: dive boat layouts proven on Gili Air — the deck arrangements the viewing-hull variant borrows from.