Camping/Beach/Outdoor Gear: Pack your beach gear so that when you want to go in the water for a swim or to snorkel you will have the things you need. A swimsuit, no nude beaches. A hat for keeping your head cool. Flip-flops to walk around in. Beach/water shoes to avoid the rocks in the sand and maybe even sunblock.
The weather is nice year round here...but you might wanna bring some layers for the evening hours dependent on the time you come...it can get quite 'fresh' sometimes.
Toiletries and Medical Supplies: Prices for these items are HIGH! Try to remember all you'll need...and those you just might need as well.
Photo Equipment: The views from many places on the island are gorgeous! You won't want to forget them...DON'T forget your camera!!
Clothing/Shoes/Weather Gear: Bring water socks/shoes or some type of foot protection for when you're in the water. Most of the beaches on Catalina are very rocky and rough. Your feet will thank you.