On Booking Manager Portal you can book a boat without the need to have the full client info.
Login to the portal, perform the search and proceed to booking like you normally would where you have the option to select between providing full client info or no client info.
In case you haven't got full client info select No client info (1.) and just enter the client Name (2.) and Surname (3.), after which you proceed to either Send offer (4.), Open option (5.) or place a Direct booking (6.) in usual manner as always.