Water is nearly 1000X as dense as air - 10,000 feet of rolling through air is close to 10 feet of travel through water, or, in this case 100 foot wide canal, so, closer to a 100,000 ft runway equivalent.
Certainly some amount of speed bled off before the belly flop. Maybe it did a little skip?
It looks from the photos that there is pavement to the water's edge, unless they painted the sod an asphalt color with chevrons.