Pregnancy and boating
It's statistically likely she will be just fine, however... For any woman, boating, skiing, or couch-potato-ing, the highest rate of miscarriage is in the first trimester, or the first 16 weeks. Should she go, there probably won't be a problem, but I don't know that for sure! If my crystal ball is working properly. However, if she does go on the trip, and have problems, then she may feel guilt for this. So it's a personnel choice.
I backpacked with my first fetus up till 28 weeks, and tele skied up till 32 weeks with my second, and they're fine and all, other than being teenagers. I know lots of moms who did, and were fine also. I also have stories of ladies who did absolutely nothing dangerous or scary, with very sad outcomes. At that gestational age, those little critters are pretty well protected by the fabulous, amazing Mom Body. An oar to the abdomen might not be the best for Mr or Ms Fetus. Lifting a 16 foot self bailer into the back of a truck, probably not so good either.
As a health care professional, and from a legal stand point, I'd have to say no go. As a mom who takes a chance with her own life now and again, I'd say, it's up to her.
L&D nurse for 20 years, ICU nurse for 8 before that. damn. I'm old.