why is my dialog menu not appearing?

integer Channel;
key av;
FindGroundOrWater()
{
 vector vTarget = llGetPos();
 vTarget.z = llGround( ZERO_VECTOR );
 float fWaterLevel = llWater( ZERO_VECTOR );
 if( vTarget.z < fWaterLevel )
 vTarget.z = fWaterLevel;
 llSetRegionPos(vTarget);
}
default
{
    on_rez(integer x)
    {
        Channel = (integer) ( "0x" + (string) llGetOwner() ) - 13579;
        llListen(Channel, "", "", "");
        llDialog(llDetectedOwner(0), "Select An Option", ["Surface"],Channel);
    }
    state_entry()
    {
        av = llAvatarOnSitTarget();
        Channel = (integer) ( "0x" + (string) llGetOwner() ) - 13579;
        llListen(Channel, "", "", "");
        llSitTarget(<0.5,0,0>, ZERO_ROTATION);
    }
    listen(integer chan, string name, key id, string msg)
    {
        if(msg == "Surface")
        {
            llSetClickAction(CLICK_ACTION_SIT);
            if(av)
            {
                FindGroundOrWater();
                llUnSit(av);
                llDie();
            }
            else
            {
                llOwnerSay("Touch To Teleport To Surface");
            }
        }
    }
}