Seawater:
◦ contains 30-35 parts per thousand salt ions.
◦ has the same proportion of salt ions world-wide irrespective of total salinity.
◦ is 3.0 to 3.5% salt on average.
◦ contains chloride, sodium, sulfate, magnesium, calcium, and potassium ions.
◦ dissolves oxygen more readily than carbon dioxide.