I plan on traveling to Phuket near the end of June and I love snorkeling. Would the monsoon season, with the rain and heavy wind, render the beaches and islands unsuitable for this activity?

Can you see many fish snorkeling in Phuket?

The monsoon rain brings rain from across the Bay of Bengal and the waters get very clouded, for snorkeling that time of year Koh Tao in the Gulf of Thailand would be much better. Though accommodation in Phuket would probably be cheaper as many hotels almost empty, for a variety of reasons.

We just got back from a Phuket vacation and went snorkeling once. the water was pretty cloudy so I think the advice of the previous poster is good. The snorkeling just isn't likely to be great in June, and the beaches have a lot of waves (better for stronger swimmers and those who like body surfing.) Good luck.