The ornamental design for a flotationdevice, as shown and described.
FIG. 1 is a front perspective view of a flotation device, according to one embodiment;
FIG. 2 is a front view of the flotation device illustrated in FIG. 1;
FIG. 3 is a rear view of the flotation device illustrated in FIG. 1;
FIG. 4 is a top view of the flotation device illustrated in FIG. 1;
FIG. 5 is a bottom view of the flotation device illustrated in FIG. 1; and,
FIG. 6 is a right side view of the flotation device illustrated in FIG. 1, the left side view being a mirror image of the right side view.
The broken lines are directed to environment and are for illustrative purposes only and form no part of the claimed design. The thin solid lines illustrate the contour of the claimed design and are not a claimed surface pattern.