Comparing or compared

[Freeguy]

Every drop of water in the ocean, even in the deepest parts, responds to the forces that create the tides. No other force that affects the sea is so strong. .......... with the tides, the waves created by the wind are surface movements felt no more than a hundred fathoms below the surface.

Between "comparing" and "compared", I'd choose the latter. However the answer key went for "comparing". Would you please tell me when we use comparing and when we use compared at the first of the sentences? It's a bit tough for me!

Thanks.

 

[Gillnetter]

Every drop of water in the ocean, even in the deepest parts, responds to the forces that create the tides. No other force that affects the sea is so strong. .......... with the tides, the waves created by the wind are surface movements felt no more than a hundred fathoms below the surface.

Between "comparing" and "compared", I'd choose the latter. However the answer key went for "comparing". Would you please tell me when we use comparing and when we use compared at the first of the sentences? It's a bit tough for me!

Thanks.

I would opt for "compared" also as it is the correct response.
Black, compared to white, is much darker.
They were comparing the merits of each automobile.