I wouldn't recommend neon for a boat. Hi voltage transformers would
probably cause a lot of interference with your electronics, fragile
glass tubes very likely to break, etc. LED rope light would work well.
Have you looked into EL lights? Electroluminescent "wire"? See:
http://www.coolight.com/category-s/1.htm. This stuff is really neat,
and would probably do exactly what you want.