Using INITIAL_MODE and LOITER for ArduBoat?

I would like my boat to automatically start in LOITER mode (set on current position) when I ARM it. Can this be set up using INITIAL_MODE set up for LOITER? The ArduRover documentation does not list LOITER as an alternative setting for INITIAL_MODE (http://ardupilot.org/rover/docs/parameters.html#initial-mode)

If INITIAL_MODE does not work, is there another to achieve the same result?