Just like any other mammals on earth, giant pandas can and do swim. They can wade into the water and swim across a river, the same as you see their close relatives like brown bears, black bears, and polar bears from all the cartoons on the TV.
However, since giant pandas live in the deep mountainous areas with an altitude of 2500 to 3000 meters where only small rivers and creeks exist, mere wading is enough to cross rather than swimming. No cute picture of giant pandas swimming!