From reading the letter it appears it is a 50% refund and a 50% future cruise credit. It must be so disappointing for the passengers on board, however, they have still received all of the Regent 'hotel' facilities (unlike when a cruise is cancelled) so it seems reasonable to me.   it would appear though that these extremely strict biofouling rules are going to have a significant impact on all future cruise by all cruise lines to this area of the world.