Hi, I am an experienced amateur...but this is not intended as a 'how do I do it myself' question
"Boat Cable" is similar to NM cable, but its intended application is for the electrical wiring on a boat. The big difference in the conductors themselves is that _stranded_ copper wire is used, nominally to provide better reliability in a high vibration environment, and the conductors are tinned, to provide better corrosion resistance.
The cable is certainly made to _different_ standards than NM or UF; for example the single conductor marine grade 14ga wire that I have at my desk is printed 105C DRY 75C WET OIL RESISTANT...TEW 105C or AWM... suggesting a higher temperature rating in harsher conditions than the THHN found in NM. The cable is also probably more flexible and less prone to mechanical damage in cold weather. The outer cover of the boat cable in the picture above is quite likely UV resistant, but I doubt that the cable is rated for direct burial the way UF would be.
One _significant_ difference is the stranding of the conductors and the tinning of the conductors. I bet that the various terminations in wire nuts or on the back of the receptacles have rather different performance and reliability characteristics with this finely stranded wire than with the relatively stiff strands found in regular THHN or THWN or the solid wire that would be found in 12ga or 10ga UF.
A link to a supplier: http://www.ancorproducts.com/Products/menu_links_products/menu_LP_wire_cable.html