use the "stitch" tool. (A) on your keyboard... click on a point on one part and stretch a line over to where you want to connect. Also stitch in new splines where needed. Then shape the resulting mesh into what you are wanting.
I still have to add the footprints in...and I have an email from the director wanting to change the skies in all of the background plates, so I guess this shot is still a work-in-progress...
http://www.zandoria.com/castaway/X188C.mov
This is a small clip from some of the VFX shots I'm working on for Miss Cast Away
The water splash is an A:M spriticle, the shot was put together in aftereffects.