The Transport Accident Investigation Commission of New Zealand (TAIC) has published its investigation report on the power loss of the commercial jet boat Discovery 2, which then caused it to crash into a canyon wall in Otago on February 25, 2025.
On the said date, Discovery 2 was operating in Skippers Canyon, on the Shotover River, with 11 passengers on board.
Shortly after commencing the return leg of the journey, and as the boat completed a right-hand turn, its engine suddenly cut out. The driver immediately reset the ignition, but the engine would not start, so the boat had no propulsion and no thrust to provide steering control.
As a result, the boat continued across the river, where it made heavy contact with the canyon wall. The boat’s speed upon impact was estimated to have been between 16 and 19 knots.
The sudden stop caused the passengers to be thrown forward and resulted in one passenger fracturing their wrist and several passengers suffering deep cuts and bruising. Two adults and two children from the same family were evacuated by helicopter.
The TAIC said some of the passengers reported significant psychological trauma following the accident.
The driver lost control because the engine suddenly shut down, leaving the boat with no thrust and therefore no steering capability.
Tests ruled out contamination of the fuel and the lubricating oil as contributing to the accident. Relevant properties were consistent with their grade specifications (requirements and limits that define the properties and quality of a product, ensuring it performs correctly and meets safety and environmental standards).
TAIC said it is virtually certain that the engine shut down because part of the engine’s wiring harness (an assembly of electrical cables or wires that transmit signals or electrical power throughout an auto-electrical installation) had chafed against a casting edge (finished edge or imperfection of a mould-cast product) of the engine. The chafing exposed a wire and eventually caused a short circuit (when an unintended path with low resistance is created in an electrical circuit, allowing the current flow to bypass the load) when it contacted part of the engine.
This resulted in the loss of the five-volt reference voltage (a stable, low voltage supply from the engine control module that powers various sensors such as the throttle (pedal position sensor), camshaft and crankshaft sensors) shared by the critical engine sensors, and the engine shut down.
The padding requirements, prescribed in the Maritime Rules for commercial jet boats, did not include enough detail to form a measurable standard for passenger protection. Padding of the seats and surrounds of Discovery 2 did not adequately protect the passengers from injury during a sudden stop.
The TAIC added that passengers were not informed of, and therefore were uncertain about, what was an appropriate brace position for an emergency on board a jet boat. It is likely that some passengers suffered worse injuries due to this uncertainty.
Operators conducting thrill-type trips (commercial jet boat operations in which spins, extreme turns, and similar manoeuvres are undertaken, as described in Maritime Rules Part 82: Commercial Jet Boat Operations – River) should inform passengers of the risks involved so that the passengers know when things are going wrong, and how best to aid themselves.
The TAIC has also warned that single-engine jet boats are vulnerable to loss of control, because once the engine fails, a jet boat has no steering.
Also, safety solutions are unique to each operator. Preventive maintenance and survivability measures are critical when redundancy is not a viable option.
