The ornamental design for a swimmingassistancedevice, as shown and described.
FIG. 1 is a front elevation view of a swimming assistance device according to a first embodiment;
FIG. 2 is a rear elevation view thereof;
FIG. 3 is a left side elevation view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a first perspective view thereof; and,
FIG. 8 is a second perspective view thereof.
The broken lines showing of the swimming assistance device is for the purpose of illustrating portions of the article that forms no part of the claimed design.