If you cancel the vehicle enter event, the server does not see you as having moved and you will appear to "teleport" back to the location you attempted to enter the vehicle from UNLESS that vehicle is a boat, in which case you are teleported to an area above the boat.

The reason that this is important is because you can abuse this feature to gain access to areas in which you do not have permission to enter. Even if all forms of movement and teleportation are canceled, you can effectively teleport from boat to boat and bypass other event controls. To fix this, canceling the vehicle enter event for boats should put you back to where you first tried to enter.