As I mentioned I'm just reading "His Needs Her Needs" and it says that "Recreational Companionship" is a top 2 emotional need for men. Therefore, he's probably inviting you boating for that reason, that he'll feel very good for having you along.
Now if you know you're not going to enjoy it and you're going to be miserable, then I would NOT go, but one suggestion would be to offer up something else you can do together that he can look forward to. i.e. "I'm going to pass on boating Saturday -- I really don't like getting wet. How about on Sunday we go for a (bike ride, hike, walk around town, walk on the beach) etc."
You've said in the past that he tends to sit in silence when you're together and looking to have a conversation. One other stereotypical male "trick" is to get him involved in an activity first. Once he's doing the activity, he may start talking. That's why walks can be good. You may find if you go for a walk he'll start opening up.
Accuray
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015
