The ornamental design for a waterbottle, as shown and described.
FIG. 1 is a top, front and right side perspective view of the water bottle showing my new design;
FIG. 2 is a front elevational view thereof, the rear elevational view being identical and shown with environment in broken lines of an unclaimed closure;
FIG. 3 is right side elevational view thereof, the left side elevational view being identical;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
The broken line showing of a closure is included for the purpose of illustrating environment and forms no part of the claimed design.