Fish Extender refers to something that is hung from the fish outside your stateroom door. Often within a cruise meet, people will get together to have an FE exchange where they give each other little gifts in the extender that is hung outside their door. There are websites to buy an FE or people make them themselves. If you are interested in participating in an FE exchange, you need to sign up to be in a group. My family has done it on all of our cruises and love it. It is just a little bit of extra magic on your cruise. If you are interested, google fish extender in google images and you will get a lot of ideas on what they look like.
We are very close to you. We live in the Canton area.