Yeah that place is great. I have seen the tide drop much lower than what it shows in the above photos. You have to time it with a lunar neap tide and then that beach is really amazing. At very low tides all of the rocks are almost completely exposed and the critters have no where to go. I have seen blennies trapped in the tidal pools before too.
Just be sure to check the tides for St. Augustine Beach before you go. Low tide at Washington Oaks will be +/- 30 minutes from St. Aug Beach. The lower the tide the better. During high tide almost the entire beach disappears.
I've been thinking about doing some snorkeling there but I think the rocks would make it extremely difficult, not to mention how shallow it is out there.