Question About Controlling Character While Using the Water Plug-in

I creat a boat and use the water plug-in to creat a sea,my boat have buoyancy component。the worst thing is that,the boat float very nice,but when i walk on the boat,if my charater location Z is 100,and i do not control my charater,my charaters location Z will be 100 forever,the boat will never change my charaters Z location,my boat make no different to my charater。 if the boat is under water,mycharater walk on my boat,my boat will never float up,my boat will be under water forever。if my charater`s capsule component is simulate physics,the problem is gone。but i can never control my charater。what can i do,i want a boat,that i can walk on it,because of sea waves,my charater can swing up an down with it