Packing for the Baths
Clothing/Shoes/Weather Gear: Water shoes were very useful for the walk between Spring and Devil's Bay
If you have swim shorts with waterproof pockets or one of those money things you can hang around your neck, you might find it useful as there are no lockers at Devil's Bay although you could lock it up at Spring Bay and head back there before leaving.
Toiletries and Medical Supplies: Sunscreen, there is a little shade but you'll spend most of your time in the sun
Camping/Beach/Outdoor Gear: Snorkel gear isn't rented there, I didn't even use mine, I don't think it's necessary to lug along