This video documents an ambitious project to build the world's fastest personal underwater vehicle, conceived as a dual-mode jetpack and scooter, with the ultimate goal of outrunning a shark. The creators aim to surpass the 79 kg of thrust from the leading commercial model, selecting two powerful electric motors capable of a combined theoretical 100 kg of thrust. The design prioritizes safety, incorporating a custom magnetic throttle, a dead man's switch, and a kill cord. Constructed from 3D-printed parts and polycarbonate sheets, the vehicle houses its electronics in a central waterproof tube with external, water-cooled motor controllers. Initial testing reveals critical control flaws that lead to a catastrophic failure of the main electronics—a period dubbed "integration hell." After rebuilding and redesigning the controls, the team successfully tests the vehicle in a pool, discovering the scooter configuration is far more hydrodynamic and faster than the jetpack. However, the project hits a major roadblock when the highest power setting consistently fails, causing the motors to shut down. The video concludes on this cliffhanger, promising a fix and a full-power test in a future installment.
Building the World's Fastest Underwater Jetpack
0:00:02 Goal: Outrun a Shark: The project's objective is to build an underwater vehicle faster than the 25 km/h Aquadart 770 Extreme, setting a benchmark for escaping a fast-moving shark.
0:01:26 Thrust is Key: To achieve high speeds, the team tests motors to beat the Aquadart's 79 kg of thrust. After an initial motor fails, they select two larger motors that produce a combined theoretical thrust of 100 kg.
0:03:12 Safety-First Design: The vehicle is designed to be both a jetpack and a safer underwater scooter. It incorporates multiple safety mechanisms: a magnetic hall-effect throttle, a "dead man's switch" that must be held to accelerate, a "kill cord" that shuts off power if the rider detaches, and protective guards over the propellers.
0:06:58 3D-Printed and Hybrid Construction: The vehicle's frame is built using 3D-printed parts, six metal rods for structural integrity, and clear polycarbonate sheets. Hydrodynamic domes are added to the front and back to reduce drag.
0:11:33 "Integration Hell" Causes Major Setback: During initial testing, a faulty waterproof button makes the vehicle uncontrollable underwater. While attempting a fix, the team accidentally destroys the custom power board, both motor controllers (ESCs), and the battery management system (BMS), forcing a complete rebuild of the electronics.
0:12:46 Redesigned Control System: After the rebuild, the faulty button is replaced with a quintuple-click function on the dead man's switch to change speed modes. Four LEDs are also added to provide a clear visual indicator of the current power level.
0:14:11 Scooter Mode Proves Superior: In-pool testing reveals the jetpack configuration is significantly slower due to the high hydrodynamic drag created by the rider's body. The scooter configuration, where the rider is towed behind, is much more efficient.
0:16:34 Partial Speed Test Results: At Speed Mode 3 (out of 4), the scooter achieves a top speed of 10.8 km/h. While much faster than a human swimmer, this is still far short of the project's goal.
0:17:13 Maximum Power Failure: The project hits a critical snag when testing the highest setting, Speed Mode 4. The motors immediately shut down upon acceleration, likely due to the electronic speed controllers being overwhelmed by the immense power draw.
0:17:41 To Be Continued: The video ends on a cliffhanger, with the team unable to test the vehicle's true top speed. They promise to solve the power issue and conduct a full-speed test in a follow-up video.