Hail Mary passes
What is a "Hail Mary" in football?
A "Hail Mary" pass is a very long forward pass into the endzone, made in the last seconds of the game. It is the sort of pass that would need a miracle to succeed, thrown at a time when there is no chance of any other play being successful.
By extension, the expression is used for any improbable effort made out of desperation.
-The Fact Monster