Review the item:
The hungry shark swam beneath the unsuspecting surfer and began to position itself for an attack. Then the fish noticed the hot pink toenail polish on the foot that dangled over the surfboard and losed its appetite.

The third verb, losed, is the problem. This sentence requires the simple past of lose, an irregular verb. Lost is the correct form; losed is a spelling error.

Verb Simple
Present
Simple
Past
Past
Participle
lose lose(s) lost lost

Swam, the verb you chose, is perfectly correct. Before you continue, review the rules for irregular verbs.

Try again to become a champion!