Cutting in half

What is the best way to cut a mesh in half? I have a mesh of the hull of a boat and the geometry follows the curve. I need to cut it in a way that crosses my lines. I was wondering if there was a boolean operation for this sort of thing maybe. Like take a plane and use it to cut an object where the plane intersects.

To my understanding Booleans only work with Solid meshes. So they cannot be used with a single plane. If you want to check them out start here: http://wiki.blender.org/index.php/Manual/Booleans

You can also just use the Internal Knife tool (K key) to add a cut line to your mesh. http://wiki.blender.org/index.php/Manual/Edge_and_Face_Tools#Knife_Subdivide

There is also an old script that will allow you to use a Plane as a knife.(Site is French) http://cobalt3d.free.fr/didacticiel/blender/tutor/images/python/knife_in_color/knife_color.py