The ornamental design for a submersiblepump, as shown.
FIG. 1 is a top perspective view of a submersible pump showing my 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;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a bottom perspective view thereof.
The broken lines shown in the figures attached hereto are included for the purpose of illustrating portions of the submersible pump that form no part of the claimed design.