I keep Oberhasli goats and mini-Obers (cross with Nigerian Dwarf). The Oberhaslis are willing to walk in
water or cross it, and will sometimes wade through mud up to their bellies on our farm. They hate doing it, but for the right incentive (some particularly tasty vine or bush), they think it's worth it. However, they're very susceptible to our hot, humid climate and parasites. The hybrid cross with the Nigerian Dwarf goat is better off in our summer weather, and more parasite resistant, but also more water-avoidant. They're also very short. A 2 foot creek is dangerously deep water for them. Not a breed I recommend for swamps; perhaps crossing a water-tolerant breed like the Oberhasli with a tall, heat-tolerant breed could provide useful results?
Also, goats are vulnerable to broken limbs or puncture wounds from slipping on debris as they climb around the brush in a swamp. Infection happens fast in those conditions, and if they fall into the mire, they may not be able to get free. I don't know how much of a hazard snakes are in your area, either, but here the water-dwelling snakes are our most aggressive and venomous snakes. Most goats don't come from regions where that's a common threat, so they don't have much instinct about that.
At the least, I would want a place that is dry where my herd would gather in the evenings, such that I could do a head count and quick daily visual inspection for injuries.