How does oxygen get into deep water and how does it get into shallow water?

It gets in deep water by seaweed and in shallow water by plants ana algae

Explanation:

Dissolved oxygen can enter the water as a byproduct of photosynthesis. While most photosynthesis takes place at the surface shallow water by  plants and algae, a large portion of the process takes place underwater by seaweed, sub-surface algae and phytoplankton.

geologic time scale (for gradpoint) =)

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.