This is the prototype of the Sea Lion, a Mazda 13B rotary engine-powered amphibious vehicle that was developed by engineer Marc Witt to break the speed records on both land and water for amphibious vehicles.
It’s said to be capable of 60 mph on the water and 125 mph on the land, but with a series of planned (but never completed) upgrades it would theoretically be capable of 180 mph on land – an astonishing pace for an amphibious vehicle.
Fast Facts: The Sea Lion Amphibious Prototype
- The Sea Lion is a hand-built, one-off amphibious prototype designed by engineer Marc Witt with the goal of setting speed records on both land and water. It’s powered by a 174 bhp Mazda 13B rotary engine, it can reportedly reach 125 mph on land and 60 mph on water, with planned upgrades offering even greater potential.
- Developed from scratch between 2006 and 2012 by M. Witt Applied Design, the Sea Lion uses a TIG-welded aluminum monocoque chassis and modular stainless steel flotation pods. Its bespoke suspension includes hydraulically retractable wheels and a deployable front spoiler for aquatic use.
- The prototype’s interior is stripped down and designed for single occupancy, with both a center-mounted control stick for water navigation and a standard steering wheel for road driving. Unlike commercially available amphibious vehicles, the Sea Lion was built purely for performance and speed, not practicality.
- Initially offered for sale in 2012 and now listed again by Mecum Auctions, the Sea Lion remains in original condition with its 13B engine and jet drive intact. Although never officially timed for a record run, it is widely regarded as having the engineering foundation to break existing amphibious speed records.
History Speedrun: The Sea Lion
The Sea Lion is a one-off amphibious sports car developed by engineer Marc Witt, whose ambition was to claim the land-and-water speed record for amphibious vehicles. Built almost entirely by hand over several years, the Sea Lion is essentially an engineering experiment to see just how fast a single vehicle can travel on land and then on water.
Above Video: This video includes footage of the Sea Lion both on land and in the water, and gives an excellent overall look at just how it works.
Development of the Sea Lion began in 2006 under Witt’s company, M. Witt Applied Design. Rather than start with an existing platform, Witt developed the Sea Lion from the ground up using CAD modeling, CNC machining, and extensive fabrication work.
His target was the Guinness-recognized Amphibious World Speed Record, which at the time was fiercely contested by around two dozen highly-specialized builders worldwide. The idea was to build a car that didn’t just float or crawl through water, but that could compete with performance cars on land and speed boats on the water – from an engineering perspective it’s a huge challenge.
The Sea Lion was completed in 2012 and offered for sale through Fantasy Junction, a California-based specialty dealer, for $259,500 USD. Witt’s intention was to pass the baton to a new owner who could continue development and potentially chase the record, which stood at 125 mph on land and 60 mph on water for that class.
As a one-off prototype, it was sold with the understanding that the buyer would be acquiring not just a car, but an experimental platform for ongoing performance development.
The Sea Lion has a TIG-welded 5052 aluminum monocoque chassis with modular stainless steel pods on the sides for flotation and lateral stability. The exposed aluminum construction hints at its aircraft-inspired design, with laser-cut and plasma-cut components used throughout.
It uses bespoke suspension that includes hydraulic retractable front wheels for improved water clearance, the front lip spoiler also rises up into an elevated position for use on water.
Development of the Sea Lion began in 2006 under Witt’s company, M. Witt Applied Design. Rather than start with an existing platform, Witt developed the Sea Lion from the ground up using CAD modeling, CNC machining, and extensive fabrication work.
Power comes from a 13B rotary engine sourced from a 1974 Mazda RX-3, producing somewhere in the region of 174 bhp. Power is sent to the rear wheels through a 5-speed manual gearbox. At the time of completion, Witt claimed the Sea Lion could reach 125 mph on land and approximately 60 mph on water.
However, plans were laid out for a possible upgrade to a Mazda Renesis rotary engine from the RX-8, with power potential ranging between 250 and 300 bhp in naturally aspirated form, and even more if turbocharged. With proper gearing, Witt suggested land speeds could approach 180 mph, though this has not yet been attempted and the Mazda 13B engine remains in place.
The interior of the Sea Lion is sparse and entirely functional, designed for single occupancy only in the interests of weight and space savings. It uses a center-mounted fighter jet-style control stick for control on the water, and a standard steering wheel on land.
Unlike other amphibious vehicles like the Gibbs Aquada or Hydra Spyder, which focus more on versatility or novelty, the Sea Lion was designed with only speed in mind. It occupies a very narrow niche in the broader history of amphibious vehicles – closer in spirit to motorsport prototypes than consumer products.
And while it hasn’t yet claimed an official record, it’s widely believed that it could break both records with the right additional engineering input – the main issue is that it needs more power – all other aspects of it work as designed on land and water.
Only one Sea Lion was ever built, after its initial listing for sale in 2012, it periodically resurfaced in enthusiast forums and auction listings. Witt has remained available to provide technical support and custom parts fabrication for any future development by a new owner.
Now For Sale: The Sea Lion Prototype
The Sea Lion is now being offered for sale out of the ownership of the Klairmont Kollections Museum in Chicago, Illinois. It remains in complete condition, with its Mazda 13B rotary engine in place, and its modified Berkeley 12 JC jet drive pump for power on the water.
The interior of the Sea Lion is sparse and entirely functional, designed for single occupancy only in the interests of weight and space savings. It uses a center-mounted fighter jet-style control stick for control on the water, and a standard steering wheel on land.
The car has been on display for a time, and it’s likely that it’ll need some refurbishment before the new owner attempts any driving – be it on land or water. Depending on who buys it, it will likely either join a private (or public) collection, or (hopefully) it might have its development continued for chasing that world speed record.
It’s now due to roll across the auction block with Mecum on the 20th of September, if you’d like to read more about it or place a bid you can visit the listing here.
Images courtesy of Mecum
Articles that Ben Branch has written have been covered on CNN, Popular Mechanics, Smithsonian Magazine, Road & Track Magazine, the official Pinterest blog, the official eBay Motors blog, BuzzFeed, Autoweek Magazine, Wired Magazine, Autoblog, Gear Patrol, Jalopnik, The Verge, and many more.
Silodrome was founded by Ben back in 2010, in the years since the site has grown to become a world leader in the alternative and vintage motoring sector, with well over a million monthly readers from around the world and many hundreds of thousands of followers on social media.
