My boyfriend asked me to attend a Formal wedding for one of is co workers and friend. It is taking place somewhere between 2 - 4 pm (B-friend has no clue) anyway it is on a boat with cruise, with the reception following at 6 pm at a country club golf course. The invitation states FORMAL. What would be the best attire to wear? Or should I wear a cocktail dress to wedding then change into a formal evening gown later?

First, you'd better find out for sure the times of the wedding and reception, or you might end up dressed formally with no place to go.

What to Wear to a Wedding (http://fashion.about.com/cs/tipsadvice/a/weddingguest.htm)

I recently attended a friends wedding.
It was an outdoor wedding but 'Formal attire' was required.
I wore a blue knee length cocktail dress... it was just a simple dress but you can take along some fancy jewellery to jazz it up.
When you drive past, check out what the other people attending are wearing as to whether you put on the fancy jewellery or not ;)