Here's the entire скороговорка about Greka and the crawdaddy/crawfish/crayfish, with the soft R's in red and the hard R's in blue:
Ехал Грека через реку
Видит Грека - в реке рак
Сунул Грека руку в реку
Рак за руку Греку "цап"!
Greka was riding (on a boat) through the river.
Greka sees a crayfish in the river.
Greka stuck his hand in the river.
"Snap" went the crayfish, on Greka's hand!