"When I first came here, this was all swamp. Everyone said I was daft to build a castle on a swamp, but I built it all the same, just to show them. It sank into the swamp. So I built a second one. That sank into the swamp. So I built a third. That burned down, fell over, then sank into the swamp. But the fourth one stayed up. And that's what you're going to get, Lad, the strongest castle in all of England."
This is a Marsh, in Not-England.
As an additional point, Communism would be difficult to implement as a member of the nobility.
But: The irony would be worth it!
So. We have all that a marsh ecology and geology has to offer (read: Not much, except some fishing, hunting, and perhaps collecting peat/tar/bog iron/etc depending on type), plus a road, plus a bit of marginal agriculture. Did I miss anything?
First priority, don't starve.
Locate someone with a bit of respect for authority and ask to stay in their house for the time being. Help them out some in exchange for room and board if we must--it's not like the other nobles can see us!
When we have time, travel along the length and breadth of our fief, talking with any locals we see about settlements, neighbors, resources, dangers, wildlife, etc. I have a few potential business models in mind, but each is dependent on certain variables being right--climate and wildlife, or where the road leads, or the kinds of crops we have, or something.