Swamps are not easy to design as the pipe tends to either sink and keep sinking or it floats and needs to be held down. You to really do your geotechnical homework on "swamp" crossing.
Rivers are the same - there are so many issues and variations, local regulations, environmental restrictions that you really need to have some experienced engineers or consultant company do this. It's not something some just picks up from a few articles or the internet.
You offer no data on this so I can't really give you any particular guidance, The question is far too broad for this type of forum.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.