How salty does the sea have to be for an egg to float?
Fresh eggs will sink to the bottom of a container filled with fresh water (no salt dissolved in it). This is because an egg is more dense than fresh water. Density is a measure of mass per unit volume, most commonly expressed as grams per milliliter. Fresh water has a density of 1.0 gram/mL, so an egg must have a density of >1.0 g/mL. Saltwater from the ocean, however, has a lot of salt dissolved in it, so it has a higher density than freshwater. An object will float in a liquid only when it has a density less than that of the liquid. Saltwater has a higher density, so the egg will float in the saltwater. Just how high or readily it floats depends on the difference in the two density values. Regular ocean water is salty but I suspect the egg would not actually float at the top of the water's surface. It would remain suspended somewhere mid-level in the ocean water. In the Dead Sea, however, the salt content is so high that its density is increased (it measures around 1.24 g/mL). An egg would float at the surface of the Dead Sea.