Here is the sentence:
Dangling his legs over the water, Tommy sat
on the pier and cried. Infused with his great sadness, the tears hit the
waves and attracted Marina, a beautiful mermaid. Popping out of the ocean
as sleek as a seal, Tommy gasped at the sight. While Marina’s tail
flopped against the wood, which was long, scaly, and metallic blue, she
asked poor Tommy the reason for his pain. Tommy explained that he had lost
the surfing championship, which included a scholarship to college. Assessing
his set as clumsy and inelegant, not a single compliment was received from
the judges. After Tommy bemoaned his ineptitude on a surfboard, Marina made
a proposal: She would turn him into a merman with the grace and athleticism
of a dolphin! Wielding ancient ocean secrets with a snap of her fingers,
a metallic green tail replaced Tommy’s legs! Diving into the waves,
the tail propelled Tommy through the strong surf. Ecstatic about his new
abilities, the training and advice Marina offered went unheeded.
Refusing to use conditioner, for example, the sun and
salt water soon damaged Tommy’s hair, which became dry and brittle.
A dangerous and foolhardy activity, Tommy
also insisted on head bumping the great white sharks that he encountered.
Putting straws up his nose and barking like a walrus did not make Tommy
popular when he had dinner with Neptune, Marina’s father. After thoughtlessly
scrambling endangered sea turtle eggs for breakfast, an apology had to be
made not only to Marina but also to the grieving reptile mother. One day
out on a swim, Tommy drank a root beer and tossed the empty plastic bottle
in the water. Polluting the ocean so carelessly was the last clam shell
for Marina. With an angry snap of her fingers, she replaced Tommy’s
tail with two human legs. Sinking under the waves, Tommy’s legs finally
kicked him to the surface where he gulped a much-needed breath of air. Saying
a curt goodbye, Marina’s tail slapped the surface dismissively as
she dove into the ocean depths. While swimming the mile back to shore as
a regular human being, Tommy regretted the gift that he had squandered.
Refusing to use conditioner, a participle phrase, describes Tommy. Notice, however, that Tommy is not in the sentence! His hair is here, but the boy himself is not! When a modifier has no word in the sentence to describe, it is dangling. Good job!
To fix the problem, you could rewrite the sentence like this: Because Tommy refused to use conditioner, for example, the sun and salt water soon damaged his hair, which became dry and brittle.