Thanks for your reply. My speed is 1.044 m/s. Is it low for a 0.005 (s) time step?

Can you please let me know how to calculate my bottom level and free surface level? 

At the point where it fails, I noticed that the planing hull is going down close to the bottom of the domain (it sinks) which dos not make sense and I think it might be because I wrongly defined my bottom and free surface level.

thanks again.