Simplify the following text for a Grade 5 native English-speaking person.
Original: Phelps holds the record for the most gold medals won in a single Olympics , his eight at the 2008 Beijing Games surpassed American swimmer Mark Spitz 's seven-gold performance at Munich in 1972 .
Simplified: In 2008 , Phelps won eight swimming gold medals at the Summer Olympics in Beijing . This broke Mark Spitz 's record for most gold medals in a single Olympics .