Object easing motion

hey, I had a question about trying to make a veryyyy simplified motion like:
http://www.tourism.city.osaka.jp/taste_osaka/

thing is i haven’t found it to be very simple… trying my way, a friends way, and this way:
http://www.actionscript.org/actionscripts_library/Movieclip_Object/
(using the _root._xmouse, blah blah method)

in the taste osaka thing, if you can see the boat/cruise ship, I wanted to create a motion somewhat like that, but x and y.

friend’s method: http://www.eggrollindustries.com/mouseFollowing.swf
I want the easingness sorta like that, but restrained with a margin around it like 50 pixels bigger… I’m sure you get the idea… any help would be super duper.