Hydro-Tail Black Hydrofoil by T-H Marine. The computer aided design of the Hydro-Tail hydrofoil provides a one-piece unit that will fit outboard or I/O lower units. The unique design means simple installation and superior strength to provide boats with the ultimate in total performance. Instructions and mounting hardware are included. The Hydro-Tail hydrofoil is excellent for stabilizing boats, reducing cavitation, reducing proposing, improving performance, water skiing, fishing or simply boating in general.