Though there is a kind of rental fee of 25 cents per towel. It is refunded when you return your towel. We never used this so assume it is charges to your card as you leave the ship and credited back when you return the towel.
In January 2005 on the NCL Pride of Aloha cruising the Hawaiian islands they
provided as many towels as you needed at the gangplank... just sign them out
and sign them back in when you return.. no charge..no hassle..no problem.