There are so many choices when it comes to labeling wires. Some will work way better than others especially being in the marine enviroment. In the past when I have done wiring jobs for people before I even started the work I had drawn up wiring schematics/diagrams before any work work was done. After explaining the diagrams and how the system was going to be added and approval from the owner I would find a local industrail equipment manufacturer that had the $5K printer that did heat shrink labels. I could typically give em 20 or bucks to print all the labels and a set of spares. This way when I did the job I had the right size labels for the wiring. Most big electrical supply houses will have the printers as well it might cost a lil more but well worth it to have a label that is legible and will stand up to the marine enviroment.
Just my $.02