A locking device includes a shackle member that includes an elongated shank portion, a stop portion on a first end and a latch portion on a second end. A locking head includes a locking mechanism that has an entryway to receive the latch portion and is movable between a locked state to retain the latch portion and a unlock state to release the latch portion. A head cover includes a cover portion that engages the locking head and a flange portion that extends inwardly to define an opening to receive the latch portion therethrough. A seal structure is associated with the inner edge of the flange and sealably engages the outer surface margin of the latch portion. The seal structure may be a margin of the flange portion or a separate O-ring. The lock may be constructed as a lockable hitch pin.
