The ornamental design for a boat, as shown and described.
FIG. 1 is a top, left side perspective view of a design for a boat showing my new design;
FIG. 2 is a top, rear perspective view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a front elevational view thereof; and,
FIG. 7 is a rear elevational view thereof.
The dashed broken lines are for the purpose of illustrating portions of the article that form no part of the claimed design, and the dash-dot broken lines immediately adjacent the shaded surfaces or solid lines represent the bounds of the claim which form no part of the claimed design.