The ornamental design for a waterbottle, as shown and described.
FIG. 1 is a top, front, and right side perspective view of a water bottle showing my new design;
FIG. 2 is a front elevational view thereof, the rear elevational view being identical except for the threads;
FIG. 3 is a right side elevational view thereof, the left side elevational view being identical except for the threads;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
The broken line showing of a cap in FIG. 2 of the drawings is included for the purpose of illustrating environmental structure that forms no part of the claimed design.