How did three kids build an underwater camera for £130?

A group of three boys aged ten to thirteen built a working underwater camera that records video and logs water temperature. The device runs on a Raspberry Pi 3 Model B+ and costs roughly £130 in parts.

The club that asked too many questions

Unboxed STEM Club meets every weekend. Three friends — Pinak, Vihaan, and Yuvan — show up with two dads who act as mentors. Kshitij Varma and Dr Amol Patil guide the sessions but the boys drive the questions. They treat problems as connected puzzles with many possible answers. When something fails they try another hands‑on fix.

The idea for Sensea started with a simple frustration. The boys wanted a GoPro to film beneath the surface of local ponds and rivers. The request was denied. They decided to build their own explorer instead.

Inside the sealed tube

The electronics sit inside a clear acrylic tube. One end is permanently closed with a 10.5 cm acrylic disc bonded by marine epoxy. A waterproof cable gland drilled through that disc lets the DS18B20 temperature probe pass out while keeping water out. The other end uses an expanding drain plug of the type plumbers use to check for leaks. This plug can be removed to swap sensors or recharge batteries then resealed.

A custom 3D‑printed base holds the Raspberry Pi 3 Model B+, the Camera Module 3, and the PCF8523 real‑time clock. The whole assembly draws power from a standard 5 V USB power pack. Low consumption means longer deployments.

Keeping the water out

Waterproofing was the hardest engineering challenge. The tube must stay dry at depth yet allow the camera to see and the sensor to touch the water. The team designed the acrylic tube as a transparent pressure chamber.

Before every dive they run a leak test. The sealed unit sits in a bucket of water for five minutes. If no bubbles rise the tube is cleared for launch.

A 2 kg bone‑shaped dumbbell acts as ballast. After many experiments with size and weight this dumbbell makes Sensea sink steadily to the river or lake bed. No propellers are used.

What the camera actually records

The Camera Module 3 captures ten‑second video clips. The DS18B20 sensor logs water temperature with a time stamp from the real‑time clock. Autofocus was rejected because suspended particles would confuse it. Fixed manual focus gives sharper and more stable footage.

A Python script named sensea_logger.py triggers recording, reads the temperature, and writes everything to the microSD card. Data is retrieved after the unit surfaces. The first deployments compared the River Cam with a nearby lake called Todd's Pit. The temperature logs showed clear differences between the two environments.

What comes next

The project has already won the Instructables Sensors Contest. Future upgrades may include a pH sensor for pollution monitoring and a depth or pressure sensor. AI‑powered species identification is also on the list. The same platform could monitor air quality, greenhouse conditions, or surface water from a floating buoy.

How many units are currently in use was not disclosed. The magazine issue 170 with the full build guide is available online now.