Stay relaxed and remember everything you will be doing, you have already done in the pool. People have problems because they panic. You have an instructor with you with a safe second. Even if you went under water, freak out and threw off all your gear, the instructure would hand you his regulator and you would be fine so stay relaxed, enjoy the view and have a great time. I did my certs in the ocean and even with the new introduction of current, I did just fine. I grew up on the beach and the majority of accidents can be traced back to stupidity. Lack of proper gear, no buddy, no flag etc.
Always dive with a buddy and if you are doing a shore ocean dive make sure you are with someone that is used to dealing with currents, tides, and navigating.
Diving is the most peaceful experience you can have. I love being under the water.