Sex on the beach is known to be a rather dubious pleasure. Pebbles, sand in the most unexpected places, comments of witnesses… Sex on the beach is also very expensive.
In most resort countries, one will have to pay a huge fine for such things.
For example, in France, the fine is about fifteen thousand euros. In particularly aggravating circumstances, such as shocked mothers with little kids, one can go to jail for quite a long time.
In Muslim countries and in Thailand, there is a law prohibiting ladies to appear on beaches topless and in a very exposing bikini. One has to be vigilant; otherwise you can be fined and expelled from the country.
The closer to the North you travel, the more tolerant laws regarding passionate lovers you will find. In Norway, for example, sex among icy fjords deserves nothing but a reprimand.