Although they flow near the top of the ocean, can reach depths of several hundred meters.

Although they flow near the top of the ocean, Surface Currents can reach depths of several hundred meters.  

Your answer if Surface Currents hope this helped!!!

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

enzyme speed up the reactions