Are near shore water temps colder then open ocean water temps?

Actually, -it's USUALLY the Other Way around ! But along the West Coast of the U.S., there's a natural Upwelling & Cold Current that slides DOWN the Coast, from North to South. And THAT's what brings those Colder Water Temps into the Harbors & Bays- along the Way... :)

It depends on where you are. At San Francisco, the California Current brings colder water down from the north along the coast. Also at times there is upwelling along the coast which brings colder, nutrient-rich water up from depth.

"than"

"than" is comparative.

"then" is temporal.

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