What is the oxygen percentage in sea water?

This didn't copy and paste very well, but you should be able to get the gist of data. The units 'mg/l' are equivalent to 'parts per million', which are better scale than percentage. As you can see, the value is temperature dependent. read more

Oxygen concentrations are much higher in air, which is about 21% oxygen, than in water, which is a tiny fraction of 1 percent oxygen. Where the air and water meet, this tremendous difference in concentration causes oxygen molecules in the air to dissolve into the water. read more

The percentages for a gas in air and in sea water differ due to each gas's characteristic solubility concentration. Gas solubilities vary with the temperature and salt content of sea water. Excluding water vapor, three gases make up 99.96 percent of air: nitrogen, oxygen, and argon. read more