Oceans, on average, contain about 35 grams of salt per litre of water. That's about 2 heaped tablespoons.

There is estimated to be about 27 million million tonnes salt in the ocean, 90% of which being exactly the same stuff we put on our food - sodium chloride.

In extreme areas, such as the Red Sea and the Arabian Gulf, the salinity of the surface layers may exceed 40 grams per litre.

Around the mouths of joining rivers, the saltiness (salinity) may be somewhat reduced by the inflowing fresh water.


Photo credit: M Chinnery, IOW Heritage Coast