The ornamental design fora watercontainer, as shown and described.
FIG. 1 is a front perspective view of a water container showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines in the drawing views represent unclaimed portions of a water container, which are included for the purpose of illustrating unclaimed environment only, and form no part of the claimed design.