I hear there are beautiful fish. Where is the best place for snorkeling ? Mljet island ? Korcula?Hvar?Kornati national park?(which is where the divers go, i think)
Go to Telascica Bay Nature Park. It's the best. You will see amazing sea life and even shipwrecks! http://pp-telascica.hr/ronjenje.php You can select English as the language to read info in.
You can stay at the Hotel Sali- http://hotel-sali.hr/en/accommodation/ or even better, stay in one of the small stone cabins in the nature park itself. They are private accommodations so you can rent them through one of these:
(1) www.adamo.hr
(2) www.kartolina-turist.com/english/index.php
(3) www.dugiotok.hr/en