The Scherzo: it's a Grade 4 piece, but don't worry, you're not expected to play it quite as fast as this! Dvořák wrote this piece for his own children to play, so it's perfect for improving violinists. Other movements have also been exam pieces in the past - the Larghetto, for instance, has been on the Grade 6 syllabus in the past.
"Wade in the Water is the name of an African-American spiritual first published in 'New Jubilee Songs as Sung by the Fisk Jubilee Singers' in 1901. The main chorus is:
Wade in the water. Wade in the water children. Wade in the water. God's gonna trouble the water.