Sign Specialist dotcom name is a clicky link. These guys are also known as namemyboat.com. They make decals that are premium and can survive the elements. If you screw up applying, they send you a free one to try again. 5 or 7 year fade guarantee.
I used www.letteringonthecheap.com. They have an easy to use template that will scale your lettering to fit the space you are trying to fit you decal in to. Different types of vinyl for flat or curved surfaces. Other options & tools also available.
I've always wanted to have a graphic made that was of dolphins, whales, and other sea creatures as seen underwater to place on the rear of my TT. My GF says that this may not be a good idea as someone may be looking at it so hard they don't notice that I have stopped.