The name of that body of water is World Showcase Lagoon.
In case you (or anyone) were wondering, the primary bodies of water at WDW are the following:
-Seven Seas Lagoon - Lake in front of MK
-Bay Lake - Lake on the side of the Contemporary opposite to MK; FW and WL's lake
-Crescent Lake - Lake that juts out of Epcot, connects Epcot to DHS, and is in between YC, BC, BW, and Swan/Dolphin
-Echo Lake - Lake inside DHS near 50s Prime Time Cafe and H&V
-Discovery River - River that surrounds DAK
-Lake Buena Vista - Lake behind DTD
-Sassagoula River - Lake between Lake Buena Vista and POFQ and POR
-Hourglass Lake - Lake between AoA and Pop Century
-Lago Dorado - Lake in the center of CSR
-Cayman Lake - Lake in the center of CBR
Those are the main ones. There are a couple less important ones too.