It'll be fine for snorkeling, and knowing Casio, it will probably (almost certainly) be fine for recreational diving. I've actually dived with an FW91 (also wearing my Seiko skx007) down to 20m, for shits and giggles, and it came out fine. The lowest rated watch I'll take down is a Cressi Manta, which is marked Diver's 100m. Cressi manufactures diving gear, including dive computers, so they know their shit.