Carbon trapping in oceans is directly linked to ocean acidification. When CO2 dissolves in seawater, it reacts with water molecules to form carbonic acid (H2CO3), which then dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-) essentially "trapping" the carbon in the ocean as dissolved carbonic acid. BTW, acidification leads to coral and other ocean life death.
Essentially we need to reduce our CO2 output not just try to shove it into the oceans.