My personal viewpoint is I would just wait til I arrived. I looked at their page and it doesn't look like very forgiving cancellation policy. Anything less than 3 days and you are SOL.This is the stated policy. Whether it's enforced like that in practice, I don't know.
In some destinations, where if the boat is full you just aren't going to be diving, you might have to take your chances. Curacao has great shore diving so you will be diving in clear water with lots of fish and coral whether you get on the boat or not.
- Cancellations made 7 days or more prior to the first scheduled dive day will receive a full refund.
- Cancellations and/or changes in reservations 3-7 days out will be charged a $25.00 per person administration fee.
- Cancellations received within 3 days (72 hours) are non-refundable and non-transferable. No-shows are non-refundable.