There aren't all that many properties in central London that top 5,000 square feet - and of those that exist, very few have a 50-foot garden.
So where exactly will you find this five-bedroom home, which also boasts a sauna and glazed 'winter garden' - for the comparatively low price of £3.5 million?
One giveaway is one of the other features - a jet-ski platform. And that's because Matrix Island is a 1930s steel boat believed to be the largest residential barge conversion in London.
"Located in the heart of St Katherine's Dock Marina, Wapping, it's just a stone's throw from the City of London," say agents Unique Property Company.
"The owner has cleverly added a feature room at one end of the barge which is used as a home office and is positioned in such a way, it enjoys the scenery of the local buildings and the waterscape, capped off by the beauty of Tower Bridge and really soaks up the Dickensian atmosphere of the place."
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Sitting along the water line on the lower deck are five double bedrooms and four bathrooms - panelled in a nod to the home's maritime heritage - along with a utility and the engine room.
There's a lovely double-height family sitting area with a large, suspended central wood burner, and above is dining area and more living space, along with a large kitchen that has everything you'd expect on dry land.
At one end of the barge is a newly-built office space with views of Tower Bridge, and there's even a storeroom for bikes.
One of the most stunning features is the huge winter garden - so big that it houses a large trampoline. The walls and ceiling all retract to open the space out to the rest of the deck.
And, as you'd expect, Matrix Island has stunning views across the marina.
Even on the water, though, this sort of space and luxury doesn't come cheap - although it has to be said that the same £3.5 million asking price will only buy a two-bedroom flat on dry land nearby.
However, the buyer of the barge will also have to find mooring and maintenance fees, which come to £32,000 a year.