The ornamental design for a boat, as shown and described.
FIG. 1 is a perspective view of a new design for a boat;
FIG. 2 is a top plan view of the boat of FIG. 1;
FIG. 3 is a front elevation view of the boat of FIG. 1;
FIG. 4 is a rear elevation view of the bottle of FIG. 1;
FIG. 5 is a left side view of the boat of FIG. 1; and,
FIG. 6 is a right side view of the boat of FIG. 1.
The broken lines immediately adjacent the shaded areas represent the bounds of the claim and all other broken lines are for illustrative purposes only. None of the broken lines form a part of the claimed design.