On CC, everyone runs from the ships, claims a hammock and then rarely uses it for the rest of the day. I mostly saw hammocks with towels and other items sitting in them, not people.
My sister really wanted to lay in a hammock and read a book, so she just approached a family that had a claimed hammock and wasn't using it and asked if she may use it. She promised to vacate the hammock the second they wanted it back.
The agreed. She read her book for two hours and they never asked her for the hammock back.
You could try the same thing. Most folks are pretty nice and if you ask, most would be willing to share.