This guide is not for committed exhibitionists, nor is it for the faint hearted. It's not a guide for nudists, as nudists don't usually associate nudity with sex.
I'm writing it because being naked and fucking on a remote, secluded or even sparsely populated beach is the one of life's great erotic experiences. The combination of the exhilarating freedom of being naked in the elements combines with the risk of being caught to produce an incredible sexual frisson. This guide is for not for the experienced: it's for those who are interested in trying it.
Step 1 -- Overcoming fear and timidity
You can't run before you can walk: don't expect to head down to the local beach, strip off and hit on your significant other in a trice. It won't work: you'll be far too nervous even to take your clothes off.
First of all, get comfortable being naked. While it is not always the case, women find this initial stage harder than men. So take it slow. If you have not been topless before, take a trip to a beachwear shop and buy a skimpy bikini. Then find a beach where topless bathing is accepted (stay away from "family" beaches). Try letting your husband or boyfriend slip the top off in the water first: water flowing over sensitive nipples is very sensual. Stay under water and no one will see. Next try slipping your top off while you are sunbaking on your front. When you feel comfortable doing it, flip over on your back.
What you'll notice is that you won't be stared at, provided toplessness is the norm at the beach you have chosen. You might get a few admiring looks, which you might find a bit embarrassing at first, but they'll also excite you.
Take a few trips to the beach doing this, to get really comfortable with the idea of being topless. If you feel up to it, walk around the beach and into the water topless. Get to the point where it's the norm, and it's not something that worries you. You'll both naturally start to combine all this with some mild sex play. Do this in the water, and you can have total privacy. Provide you've chosen a beach that's not densely populated, you can do it on dry land as well. Guys, caress your girl's tits and nipples, and feel her clit and pussy gently. Girls: you know what to do. In the end, you'll both rush home and fuck each other's brains out.
The next step is getting it all off. Girls, you might find this easier than your partners, as you've already done half the job. But for both of you, it's a big step: risking being seen by total strangers completely naked. There are two approaches: one is to go to an official or unofficial clothing optional beach, and joining the throng. If you can overcome your initial fear, you'll relax quickly as you'll be two of many. If that's too confronting, the other option is a deserted beach or one with hardly anyone it. These are harder to find, but I reckon that's a better option. Once the bottoms are off, you're much freer to be yourselves, horse around in the water and on the beach and so on. Other beachcombers won't make a fuss, and will keep a discreet distance.
If neither of these options works for you, try going out to a quiet beach on a warm night. But don't swim out: if anything happens, no one will be there to rescue you. Waste deep is as far as you should go out.
Once you've done this a few times, you'll be ready to take the whole thing much further, if you haven't already started, and the rest of this guide is designed to help you do just that.
Step 2 -- Choosing the right beach
Rule number one is that it needs to be remote. This usually involves a walk from the car, and it will mean a drive away from main population centres. It can be a clothing optional beach, but it's more likely to be an unofficial one than an official one, as there will be fewer people there. A thinly populated unofficial CO beach is the best: if other people are naked, you won't draw as much attention to yourselves. But CO is not essential: the most important thing is a thin spread of people. The people on it need to be sufficiently spread out so that each person can't easily see what everyone else is doing.
Rule number two is to go somewhere you won't be known: you'll be far more relaxed about this far from home, I can tell you! If you do get caught, you don't want to get caught by your friends. In fact, doing this on vacation is a great idea, provided you are able to suss out the local beaches.
Rule number three: don't choose a busy period. Labor day weekend or spring break are no nos for first timers. Even weekends are not great. Weekdays, particularly those early in the week, are good. Go early morning -- say around nine -- before many people have arrived or after four, when most have left.