No charge. I did not have to make any reservations on the Explorer or the Radiance.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08
If you read through the daily compass, it will list the hours of operation. Just go up there and sign in and wait your turn, no charge and they supply the shoes and the gear. Be sure to wear some socks.