Build Waterproof Enclosure
The submerged unit must survive continuous saltwater immersion at depths up to 30 meters. This guide covers enclosure design considerations and construction approaches.
Design Requirements
Section titled “Design Requirements”| Parameter | Requirement |
|---|---|
| Depth rating | 30m (3 atm) minimum |
| Camera window | Optically clear, IR-transparent |
| Connectors | IP68 rated, saltwater resistant |
| Material | Corrosion-resistant in saltwater |
| Maintenance | Accessible for battery/SD card swap |
| Size | Fits inside a standard crab pot |
Materials
Section titled “Materials”Enclosure Body
Section titled “Enclosure Body”Option A: PVC pipe housing
- Schedule 40 PVC pipe (2” or 3” diameter)
- PVC end caps with O-ring grooves
- Inexpensive, easy to machine, seawater resistant
- Drawback: bulky, limited geometry
Option B: 3D-printed housing
- PETG or ASA filament (UV and saltwater resistant)
- Custom geometry matches pot interior
- O-ring groove printed directly into design
- Post-process: acetone vapor smooth or epoxy coat for watertightness
Option C: Cast acrylic tube
- Clear acrylic tube with machined end caps
- Serves as both housing and camera window
- Common in underwater camera housings
- Drawback: more fragile, requires careful O-ring design
Choosing an Approach
Section titled “Choosing an Approach”Use this matrix to pick the right enclosure material for your specific component. You may end up using different approaches for different parts of the system.
| Criteria | PVC Pipe | 3D-Printed (PETG) | Acrylic Tube |
|---|---|---|---|
| Cost | ~$15 | ~$25-40 | ~$40-60 |
| Optical clarity | Poor (opaque) | Moderate (translucent PETG) | Excellent |
| Pressure rating | Good (Schedule 40: rated to depth) | Moderate (layer adhesion is weak point) | Good (if wall thickness adequate) |
| Machinability | Easy (standard plumbing tools) | Requires printer + post-processing | Moderate (needs careful drilling) |
| Recommended for | Non-camera components, base station housing | Prototyping, custom geometry | Camera viewport, submerged unit final design |
Practical guidance: For a first build, use PVC for the main body and bond an acrylic window into it for the camera viewport. This gives you the pressure rating and low cost of PVC with the optical clarity you need for the camera. Move to a full acrylic or custom-printed design once you’ve validated the electronics and seal geometry.
Camera Window
Section titled “Camera Window”- Material: Borosilicate glass or sapphire crystal
- Coating: Anti-reflective (AR) coating, IR-transparent
- Seal: O-ring compression between window and housing
Connector
Section titled “Connector”- Type: IP68 bulkhead connector (4-pin)
- Material: Marine-grade brass or 316 stainless steel
- Cable: 4-conductor shielded, polyurethane jacket
Assembly Principles
Section titled “Assembly Principles”O-Ring Seals
Section titled “O-Ring Seals”The most critical component of any underwater housing. Follow these principles:
- O-ring groove dimensions must match the O-ring cross-section exactly (consult the Parker O-Ring Handbook)
- Lubricate with silicone grease before every assembly
- Inspect for hair, sand, and nicks before sealing
- Test the seal at 1.5x rated depth pressure before deployment
Potting
Section titled “Potting”Electronics inside the housing should be potted (encapsulated) in clear epoxy or silicone to:
- Prevent internal condensation damage
- Add mechanical shock resistance
- Eliminate air pockets (which compress at depth and stress seals)
Pressure Testing
Section titled “Pressure Testing”Before deploying any enclosure:
- Vacuum test: Pull a vacuum and monitor for leaks (cheapest method)
- Hydrostatic test: Pressurize in a chamber to 1.5x rated depth
- Soak test: Submerge in a bucket for 24 hours and inspect for moisture ingress
- Indicator: Place a moisture indicator strip inside — changes color if any water enters
Validation Checklist
Section titled “Validation Checklist”Run through this sequence before you trust an enclosure with live electronics. Each step catches a different failure mode, and skipping steps has a way of costing you an ESP32.
- Visual inspection — Look for cracks, voids, uneven wall thickness, and tooling marks near O-ring grooves. Any defect in the sealing surface is a leak waiting to happen.
- Dry fit — Assemble the complete enclosure without electronics. All components should seat without forcing. Cable glands should be hand-tight. If you need a mallet, something is wrong with your tolerances.
- Bench pressure test — Submerge the sealed, empty enclosure in a bucket of fresh water for 24 hours. Place a strip of dry tissue paper inside before sealing. Any moisture on the tissue means the seal failed at zero pressure — fix it before going further.
- Shallow water test — Deploy at 2-3m depth for 1 hour. This catches slow leaks that bucket testing misses because of the added hydrostatic pressure. Inspect the tissue and all internal surfaces.
- Working depth test — Deploy at your target depth (typically 5-15m for crab pots) for 4 hours. This is the real test. Retrieve, dry the exterior completely before opening, then inspect.
- Long-duration soak — 48 hours at working depth. Temperature cycling between day and night causes thermal expansion that can break marginal seals. Only after this test passes should you install electronics.
Tether Penetration
Section titled “Tether Penetration”The tether cable must pass through the enclosure wall without compromising the seal:
- Drill a hole matching the bulkhead connector OD
- Install the bulkhead connector with its built-in O-ring
- Torque to manufacturer spec
- Apply marine sealant around the outside as a secondary barrier
- Strain relief the cable inside the housing (zip tie to a post)
Next Steps
Section titled “Next Steps”- Source materials based on your chosen approach
- Print or machine the housing
- Pressure test before installing electronics
- See Hardware: Submerged Unit for electronics integration details