First Day Following OCEARCH in Cape Cod

First day in the air over the OCEARCH vessel. They are just offshore of Shark Cove in Cape Cod.  As we approached the boat a massive chum slick could be seen trailing behind and drifting toward shore.  
On shore was a large gathering of gray seals that we circled for several minutes.  Suddenly the pilot and I spotted two white sharks swimming only yards from where the seals played in the surf. The pilot estimated the sharks to be of at least 15 feet in length.  After a time the sharks moved away from shore and straight toward the chum slick.

Upon landing, we checked the OCEARCH site to find out that the sharks did investigate the chum slick, but did not stick around.

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My first thought was "Please don't hook those sharks."  I am truly nauseated at what these sharks go through during the hooking, hauling, and bolting process.
My second thought was, "These sharks have altered their behavior due to the chum slick."  I can't prove what the sharks were thinking, but I can tell you that they were spotted near the seals and were later spotted hundreds of yards away in the boat's chum slick.  If I am correct, this means the sharks ceased their normal hunting / feeding behavior and wasted their time and energy investigating a false food source.  But it could have been coincidence.  How can we tell the difference?

Thoughts?  Reactions? Arguments?