Various configurations of improved wake-modifying devices for a power boat are provided herein. All such configurations provide a water channel and (optional) wedge for capturing and redirecting significantly more of the water flowing past the transom of the boat than conventional trim tabs consisting primarily of a flat plate. This increases the upward force applied to the deployed wake-modifying device and raises the stern of the boat on the non-surf side to list the boat to the surf side, producing a larger wake on the surf side. Some configurations provide a convergent water channel to produce longer, smoother wakes on the surf side of the boat. Other configurations provide a divergent water channel, which produces a comparatively shorter, taller wake on the surf side of the boat.