Weather and Excursions

I'm going to the Caribbean for the first time this December. My love is snorkeling and I am considering signing up for it or snorkeling+wildlife at almost every stop. But what if the weather is bad? I imagine they'd still do the excursion, but several bad days might be too many for not-quite-great day trips.

Any information on others' experience and advice? Do these excursions usually fill up pre-trip or could I wait and see about a few?

Thanks for any insight!

Some excursions do fill up quickly.

Are any of your snorkeling excursions marked as "limited" on HAL's site? Those can fill up fast.

We had a HAL snorkelling excursion cancelled the night before due to bad weather. It was on a smallish catamaran and they said it was cancelled because it was going close to shore and we couldn't do snorkelling with the expected waves. There was another excursion on a much larger boat that was still going so I went on that instead. My DH preferred the smaller boat and be closer to shore, so I went on my own and still had a good time as I didn't want to miss out.