One of the reasons I bought the 4wd Mercedes Sprinter Van Conversion was so that I could tow a 3500 lb boat and still camp. The other major reason I bought the Revel 4×4 is that I could park the 19 foot van in a regular parking space. The latter is less achievable with a 20 foot boat in tow. The boat solution was solved with the largest portaboat that would fit on the side of the van. A 12 ft portaboat is twice as stable as an 8 ft portaboat. I ordered a custom side rack for the boat from Vertirack
I also like to fish lakes and ponds with a pontoon boat or float tube. I found the best way to transport them is to strap them to the back of the van.
OhaaAnd let not forget Pyramid Lake Ladders.