Sentence 1: When Billy was five he went to the beach for the first time. 
 Sentence 3: A life guard saved him before it was too late 
 Sentence 4:  Billy took swimming lessons the next summer and learned to swim 
 Sentence 5:  When he was older he became a lifeguard 
 Option 1: A wave knocked him over and he nearly drowned. 
 Option 2: A seagull knocked him over and he nearly suffocated in the sand.