But you don't even have to do that, you could install a second wireless card in the device you are turning into a router and it can use one of the wireless interfaces to connect to the access point, and use the other one to act as an access point for devices on your boat. To do that requires some research, it can be done with Linux but I don't know how you'd do it with another operating system.
In that scenario would I even require a second wireless card? The external USB antenna/hardware combo is in effect the interface that connects to the external ISP access point. After installation of the antenna software on the "notebook" it shows itself as an active wireless hardware device under the network control settings along with the existing Local Area Connection and Wireless Network Connection adapters already built into the notebook.
Could I not "bridge" both the new antenna hardware device (which has now actively connected to the shore ISP) and the notebook's built-in wireless card as it shows itself in the Network Connections page? I understand this is achieved by highlighting both devices one wants to bridge, right clicking on them and then using the "Bridge Connections" option that comes up.
Shouldn't the netbook's built-in wireless card now act as a wireless internet access point thereby allowing me to connect to it with any other wifi device aboard my boat (computer or otherwise)?