First of all, welcome to MP ganjadude11. Good to have you here. You have came to the right place to learn and share you knowledge of growing mj. This site is loaded with people that are very knowledgeable and are willing to help you out in any way possible.
As for the plants next to a marsh, it's probably not the best place to grow mj but it will work. As long as the ground doesn't stay wet for more than a day or two at most, it should be ok. MJ is a very tough plant and can grow just about anywhere in the world. I'm sure they will do just fine. Make sure to keep us posted and we look forward to seeing some pics of your ladies sometime in the near future. Take care my friend.