This guy built a working submarine from soda bottles and PVC pipe
Some engineering projects begin with a conventional heap of metal, timber and machine tools. This one begins with objects most Australians carry home from the supermarket: empty soft-drink bottles and lengths of ordinary PVC pipe. The result is a compact, working submarine whose sealed air pockets provide lift while a lightweight frame holds the controls, camera and propulsion system in place.
The build succeeds because each part has a manageable job. Trapped air makes the bottles buoyant, while ballast lets the craft descend and rise again. PVC provides a shape that can be cut and joined with common tools, and a small motor moves it through the water. The pleasure lies in watching those simple principles combine into controlled movement, not in pretending household materials can support every use found in a professional vessel.
That distinction gives the clip broad appeal for a local audience of tinkerers, students and casual viewers. A backyard version can spark interest without needing a workshop, boat ramp or ocean. Australian conditions also make the experiment instructive: heat, sunlight, humidity and coastal salt can influence how plastic ages, how joints seal and whether a model keeps working after its first successful run.
How bottles become a floating hull
A capped bottle is an effective buoyancy module when it remains completely submerged. It displaces water while contributing very little weight, so a group of bottles creates reserve lift. The bottles do not need to withstand pressure; they mainly provide volume and stability. Their transparency is an advantage too, because a viewer can see trapped air, shifting water and the movement of ballast.
PVC supplies the skeleton. Depending on the design, sections can form a protective body around the drive train, support a camera or create channels for ballast and wiring. Ordinary PVC pipe is not a certified pressure hull, so the craft works because it stays near the surface and uses shallow, controlled dives. Calling it a submarine describes its behaviour more accurately than its structural rating.
The build also depends on careful joining. Bottle caps must be tight and their seams clean; pipe joints need compatible fittings and enough setting time. A tiny leak can change buoyancy, while an unbalanced motor can make the craft roll. The finished machine therefore looks improvised, but the successful details are familiar to anyone who has assembled a model that has to work beyond a demonstration on dry land.
The engineering behind the trick
Buoyancy is only half the challenge. A submarine must also remain stable, which comes from controlling the centre of gravity and the distribution of weight. Low components such as batteries help the craft stay upright, while adjustable ballast allows the operator to send it downward and pull it back towards the surface. If the weight sits too high, the model bobs and rolls; if too much water enters the ballast system, it may never recover.
Propulsion supplies the movement that makes those adjustments visible. A protected electric motor turns a small propeller, and careful placement keeps the craft from turning in circles. A simple rudder or vane can provide directional control, while a camera mounted near the front gives the operator a view of the water ahead. None of these systems needs to be complicated, but each needs enough clearance from the hull to avoid snagging.
Waterproofing and leak control are equally important. PVC joints can be sealed with suitable fittings, while bottle caps and seams require careful preparation. Escaping air produces telltale bubbles, and a steady stream may reveal a failed joint or a ballast tube that is passing water. Testing each compartment separately makes troubleshooting much easier than repeatedly placing the entire submarine in a bath and guessing where the problem lies.
Bottle modules and PVC compared
The material choice becomes clearer when the roles are placed side by side. Bottles contribute inexpensive buoyancy, whereas PVC supplies structure and connections.
| Feature | Soda-bottle module | PVC pipe and fittings |
|---|---|---|
| Main function | Adds buoyancy and can provide a visible air pocket | Builds a frame, housing, duct or mounting point |
| Practical advantage | Light, inexpensive and easy to replace | Versatile, widely stocked and easy to cut or join |
| Main limitation | Scratches, flexes and can leak at the cap or seam | Ordinary pipe is not designed to resist cabin pressure or impact |
| Best role in the model | Reserve lift, ballast volume and visual effect | Support and protection for low-depth mechanisms |
| What to inspect | Firm caps, intact seams and even buoyancy | Correct fittings, sound joints and protected wiring |
The comparison explains much of the video’s appeal. Transparent bottles make otherwise invisible forces easy to follow, while the PVC framework gives the craft a recognisable shape. Ordinary household parts can look convincing when their functions are clearly separated and carefully assembled.
Adapting the idea to Australian backyards
Australian hardware shoppers will find standard PVC pipe and compatible fittings at stores such as Bunnings and Mitre 10. It is generally sold in metric sizes and useful lengths, so a small prototype can be assembled without specialist machinery. Offcuts are often enough for a frame, while fittings purchased in the same trip solve the loose ends that can otherwise delay a backyard project.
Local weather deserves equal attention. Builders in Sydney need to consider salt-laden coastal air, which can corrode fasteners and damage exposed motor components. Brisbane’s intense sunlight and summer heat can degrade unsuitable PVC and adhesives, so products should be UV-rated and solvent-welded joints allowed to cure according to the manufacturer’s instructions. Melbourne’s changeable conditions can bring rapid temperature shifts, rain and condensation, all useful reminders that a model tested on one mild afternoon may behave differently in cooler water.
Australia’s container-deposit schemes provide a practical way to source and sort eligible beverage containers. Participating schemes in New South Wales, Queensland and South Australia can return eligible bottles for a refund, while damaged or unsuitable containers can follow local recycling rules. Reusing a container once does not make it indestructible, but it gives a throwaway item another useful life and can provide a steady supply of consistent bottles for ballast experiments.
The clip’s low-cost ingenuity also travels well as an idea. For a Cambodia-focused counterpart to the broader community-resource theme, CFC Cambodia offers readers a different local context and a useful international point of reference.
Watching safely and respecting the materials
A working model is not the same as a vessel designed to carry a person. Nothing should be sealed inside an occupied compartment, and a bottle-and-PVC craft should never be treated as a safe diving vehicle. Propellers can catch clothing or hands, batteries and wiring introduce electrical risks, and unexpected flooding can turn a small model into a projectile. Safe viewing means enjoying the mechanism from a secure position on dry land.
Local rules matter when testing outdoors. A home-built model should not be launched into public waterways or waterways without checking the relevant council’s rules and obtaining any necessary permission. Mains-powered equipment has no place near water, and battery-powered systems require suitable protection. Testing in a shallow container or controlled indoor pool also reduces waste, prevents accidental wildlife entanglement and makes leaks easier to contain.
Ways to get the most from the clip
- Watch how the craft changes trim as its buoyancy and ballast shift.
- Pause at the joints and look for signs of leakage, bubbles or uneven weight distribution.
- Treat the model as an engineering demonstration, never as an occupied submersible.
- Recycle damaged components and support lawful, responsible maker projects.
See the submarine come to life
Curated on Lajsiab, the unusual sequence is easy to enjoy through watch the submarine build. Repeated viewing reveals details that a fast first pass can miss: the way the craft settles before diving, the stream of bubbles from a changing ballast system, the direction of the propeller and the small corrections needed to keep it level. The transparent bottles also make its behaviour unusually easy to read.
Lajsiab’s wider archive covers technology demonstrations, music performances, automotive maintenance, sports compilations, travel humour, Japanese variety clips and other internet curiosities. Watch the submarine sequence, share it with a fellow tinkerer and support the reader-supported archive so unusual demonstrations remain easy to find.