I think the best chance of getting a waterside table is booking a PS as early as you can for the earliest seating, arriving at the restaurant at least 15 minutes before the PS time, and also requesting a waterside table if one is available.
However, I know that not all 11:30 seatings are waterside because I had an 11:30 seating and was quite far away from the water. My theory based on that experience is that we booked too late and that they might seat people in the order that the PS was made, and my guess is that they also try to accommodate people who actually ask for waterside tables (we didn't ask).
We didn't book our PS until just a couple of days in advance, and while I got the 11:30 seating and arrived 15-20 minutes early, the place was already packed with people waiting. I also noticed that there were numbers on the cards that the hostess was using to seat people and that it wasn't in order of who got there first even though many of us had 11:30 seatings.
All of that being said, while I won't deny that sitting near the water adds to the experience, the atmosphere of the restaurant is truly unique no matter where you sit, and I think the food there is quite good as well. (The prime rib is one of my favorites, as is the calamari appetizer.) I hope all turns out well for you and that you enjoy your experience there!