They do have life vests that can fit adults. Usually for those with special needs or uncomfortable swimming. They don't keep a stock that fit plus size adults at the resorts that I've seen. They do only have a limited number of vests (maybe one or two) and not always in the best condition. The one my DS used was very cracked and not the cleanest. If you find they are out of the adult size go to the front desk and they can get you one.
The adult size is located on the bottom of the left stand in photo from all star movies. Not my photo found it thru a Google search.
Yes. Some special needs or reluctant swimmer adults may need or want access to a floatation vest during their Disney visit. The resorts that have attached boating and marina recreation areas also have adult-size life vests already on hand. Simply go over to the marina area to request one. There is no charge to borrow the vest, but you may need to leave your room key or driver’s license until the vest is returned. If you need an adult vest and you’re not staying at a resort with a marina, speak to the front desk of your hotel and they will often be able to borrow one from another hotel.
Do you have sizing information for the adult vests?
Here you go:
Adult XS: Weight more than 90 lbs., Chest size 31-34 in.
Adult S: Weight more than 90 lbs., Chest size 34-37 in.
Adult M: Weight more than 90 lbs., Chest size 37-40 in.
Adult L: Weight more than 90 lbs. Chest size 40-43 in.
Adult XL: Weight more than 90 lbs., Chest size 43-46 in.
Adult XXL: Weight more than 90 lbs., Chest size 46-48 in.
Additionally, there may be a small supply of even larger vests. Inquire at your resort.