Most of the salt in the sea is classic sodium chloride, i.e. ordinary table salt. If you let some sea water dry in a bowl, you'll have enough salt for a whole barbecue in a couple of hours. Salt is a corrosive, though, so instead of drying it, count on the fact that it can also bleach and dry out your skin. This may appeal to teenagers who suffer from acne, for example.
Where sea salt comes from: It's brought in by rivers that leach it out of the rocks. Another source is lava from underwater volcanic eruptions, which dissolves the minerals back into the water by rapid evaporation.
You may also notice that your teeth are whiter after a holiday. This is because the salt dissolves the deposits during bathing.