The new 2025 Bentley Speed Continental made its global debut in Switzerland this month, but rewind three-months and it made news for a different reason, making its public debut at the UK’s Goodwood Festival of Speed, but also being the fastest car underwater.
True, and while that slightly misleading headline certainly needs explaining, the Bentley Continental GT set an “underwater” speed record of 335km/h – which is the exact same top speed quoted by the previous third-generation GT.
That’s quite impressive given the previous model was powered by a 6.0-litre W12 engine with 467kW/900Nm, and the new model run a 4.0-litre hybrid V8 with 575kW/1000Nm, given a boost by its EV motor.
The record run took 13 months of planning and preparation and happened in April 2024, in the Ryfylke tunnel in Norway: at 14.5km, the longest and deepest sub-sea tunnel in the world – so, technically, 292 metres “under water”.
Running on renewable biofuel and its hybrid battery charged with electricity from Bentley’s solar panes, the car was mechanically standard and unmodified, save for some added safety gear, beyond inflating the tyres to the correct high-speed pressures. But for the run in the confines of the tunnel, extra precautions were needed.
The first step was to secure the right tunnel. The Ryfylke Tunnel near the town of Stavanger in Norway was the perfect candidate, being relatively straight, smooth and huge reserves of road.
The local Stavanger police assisted by securing the tunnel and the permit required to exceed the speed limit. The physics of the car at top speed in a 10 metre-wide tube were simulated using Computational Fluid Dynamics, revealing that aerodynamic drag would be 11% higher in the tunnel.
The aerodynamic loadings on the car were also affected by the pressure waves and wake of the car bouncing off the tunnel walls, meaning that Bentley’s body engineers also had to assess the atypical forces on the panels around the car. Simulation showed the importance of running the car in the centre of the tunnel – proximity to the sides would accelerate the flow of air between the car and tunnel wall, creating a suction that would pull the closer ever closer to the wall – similar to the Coanda effect.
The Tourmaline Green top speed car was prepared exclusively for the high-speed runs with a roll cage and bucket seats, and its 22-inch Pirelli tyres had been x-rayed to check for any inconsistencies beneath the surface. The car was driven by former British Rally champion Mark Higgins, who also holds the car lap record around the Isle of Man TT course.
The top speed runs were carried out at 1am, when closing one of the two tunnels would cause minimum disruption to local traffic, which was routed to the spare tunnel to avoid delays. Despite the increased drag, the new Continental GT Speed accelerated from standstill to 335 km/h in just 33 seconds, and was able to hold top speed for as long as the film’s director, Jon Richards (formerly of Top Gear) required.
We will only assume this is the speedometer indicated speed, given the lack of GPS tracking in a tunnel and the apparent lack of external speed-logging equipment, and the video appears to show the GT getting to its 335km/h rather easily, relatively, suggesting there may have even been a little up its sleeve, accounting for speedo error and the differences in atmospheric pressure compared to outside in the open.
Given it generally only takes around 2km to reach 300km/h, and that there was plenty of road to eke out those extra 35km/h, the video shows it took just 9 seconds to go from 300 to 335km/h in the video, which does cut short rather abruptly at 335km/h, suggesting there was a lot more in it.
In fact, it's highly likely there was and is, with a Continental GT seeing 347km/h speed indicated on an autobahn back in 2022.
To celebrate and commemorate the unofficial underwater record, Bentley set up a Continental GT display at Goodwood with a FOShtack, with live fish, that Bentley reps recently reported suffered no marine casualties throughout the event, thanks to an on-site aquarium specialist and a full filtration system.
The back wall of the display housed a large, outdoor LED screen that played both the Underwater Speed Record launch film and a new behind-the-scenes look into how the record was achieved.
The ‘FOShtank’ is a bespoke version of the glass ‘Toy Box’ display units that Bentley utilises across it’s Dream Factory campus in Crewe, England, but modified to include two custom-built, three-tonne fish tanks containing 1400 litres of water and 30 Shubunkins and other goldfish, in a tongue-in-cheek take on the underwater theme.
The display also featured a Continental GT, while both a GT Coupe and GTC Convertible ran up the hillclimb course over four days.
In the ultimate irony, under heavy rain and wet conditions – under water, you could say - the Bentley GTC had a big spin on the Sunday of the event during one of its hillclimb runs, thankfully escaping without damage.