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.
Tiger sharks (pictured) are among the 17 species that appear to lack color vision. Sharks may be able to smell blood from miles away, but they probably don't know how red it is: New research suggests sharks are color-blind.