As someone who lives in Prague, I have a recommendation for you: NEVER jump into the Vltava (the river). It's a very bad idea. You'll drown or get hypothermia before you can swim to shore and die. 4/5 of the people pulled from the river are foreigners. Last year, it took two weeks to find the body of a Brit who jumped into the river from a boat after game of truth or dare with his his friends. :-/
The name of the cemetery is Slavín. From the word Sláva = Glory.
More than 600 prominent Czech men and women are buried here - actors, singers, writers, poets, politicians, scientists, inventors, doctors... It's like a VIP cemetery for the whole country. :-D And also a tourist attraction...