External antenna option for a macbook

hello, this is my first ever post so please bear with me! I have a white macbook purchased august last year (one of the last before the nice new aluminum ones!!)
We are cruising around south east asia on our steel boat, currently in a marina for the wet season that has free wifi. I can get great strength when sitting outside the boat but once inside (out of the rain!!) I get nothing at all. Other boats use a engenius external ariel (they all have pc's) but understand that wont work on a macbook. Does anyone have any ideas of what I can use as an external ariel so i can keep my macbook nice and dry and still use it? or maybe an alternative mac option?
Many thanks

You may need to go with an external WiFi adapter to use an external adapter. Have a look at this site, as they have a number of different options.

Thank you! I had actually found that site but was a little perplexed by all the options. Will investigate further. I was hoping there was a product like the base station that I could just sit in the cockpit, and then link to that wirelessly from inside the boat, but looks like I will have to get a little more technical on it all!!! Once again many thanks.