When 100mL of HCl are added, the pH of the solution will equal 7. Bromthymol Blue, an indicator which changes color in the 6-8 pH range is used in this case, because we can see when the pH is equal to 7.
Firstly, you have more chance of getting hit by a car or killed by a coconut falling on your head than getting attacked by a shark. A shark isn't going to pick you by what colour your boogie board is. Usually they attack people who have just gone to the toilet or are simply the unlucky ones. I think Mythbusters found that sharks are not attracted to certain colours but they tend to bite the colour yellow more once they do attack.
By raising its head several feet out of the water, a White Shark may be better able to detect airborne scents that could indicate a rich source of food in the otherwise featureless expanse of the open ocean. To what extent the Great White relies on its sense of taste is also a matter of conjecture. There are a few, scattered reports of other sharks apparently rejecting food on the basis of taste, but this has not been tested.