We went in March and it was offered. I think I do remember someone saying that March-April is not the rainy season so sometimes the water levels are too low.
__________________
Carnival Freedom June 2009
Crown Princess March 2009
Carnival Glory January 2008
Naviagator of the Seas Mar 07
Sovereign of Seas Oct 06
Carnival Glory March 2005
Nordic Empress 1996
Cyndi is correct. It is because sometimes during these months the water levels are too low. However, I have gone both in February and April with a private tour. Although there were a couple of spots where the water level was low - we just walked or floated on our tubes with "butts up" and it was fine.
Nancy