Since DCL doesn't require payment for excursions when booking them (unlike other cruise lines), often people will book excursions "just in case" and then cancel them.
If it still hasn't come through before your cruise, check at the Port Adventures desk as soon as to board to see if there's a wait list for the excursion.
There certainly is hope. First, check online 4-5 days out, when people who change their minds should have canceled the activities they don't want. (This is a good way to snag a cabana). Second, check with the port activities desk when you start your cruise, you never know.
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