As CA and Donna said, they do have life jackets, but you don't put them on to tender. They're just there in case of an emergency and I've NEVER heard of one on a tender.
If the seas are too rough the tenders won't run and you'll miss that port . I don't know your itinerary, but Grand Cayman appears to be the "most missed" port due to sea conditions.
Have a wonderful cruise and please feel free to ask any questions here. The people on this site love to help!
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