Had my son out at two weeks old and he loves the water. He is now 20 months and no problems. Do not strap the child in. If the boat flips and sinks the baby will go with it. If the car seat sinks and the baby is strapped in the baby will sink. At first we did bring the carrier to lay the baby in while we were still but not straps attached anywhere. Your wife will need to properly hold the baby in the passenger seat where it is the safest. And hydration is extremely important. Especially when it comes to the summer months. Go out early and get in early. And there are a couple things you need to be vigilant on. You may think your okay but then you get what happened in RD's story. Infants cannot regulate their own body temperature like an adult can. You need to keep the bimini up, keep the baby wet (playing in the water, dunking, keeping a wet hat on, mister etc. Always have some cool clothing on the baby. Always. And secondly, keep the baby hydrated. This is the tricky one. You will think the baby just had their normal bottle a couple of hours ago. Nope not good. The baby's body will be using all of it, feeding will need to be much more constant. Sometimes you have to feed baby before baby tells you it is hungry. You are basically feeding just to keep hydrated. If mama is breastfeeding baby then you are good to go. Whip out the boob every so often. We've got a new baby coming in June and we will do the same thing.
Anyways, talk to your pediatrician and read, read, read. Your children are your most important thing in the whole world. A little research to keep them safe is a good thing.