A gif of a swimming bat! Although there is little scientific data on the subject, observations by naturalists in the field seem to support the fact that some bats swim in stressful situations but that it is not normally part of their ordinary behavior patterns.
For example, flying foxes, often island inhabitants, may have to fly long distances to obtain food. A forced landing or a foray over water to collect fruit which has dropped and floated there may necessitate an unexpected swim. Photographs of the flying fox, Pteropus giganteus, show the animal actually swimming, using its wings and feet to reach land rather than floating or paddling. (Source)