Why didn't Odysseus' boat sink in The Odyssey?

At the beginning of The Odyssey,
Odysseus has already been shipwrecked and has been living on the island of
Calypso for quite some time.  His boat was wrecked by troubled waters created by
Poseidon who is angry at Odysseus for having blinded his son.  Athena, Odysseus's patron
goddess, intercedes and goes to Zeus on Odysseus's behalf.  Zeus tells Athena to help
get Odysseus home to Ithaca where he is badly needed.  Odysseus is then able to build a
raft to get off the island, and more of his adventures ensue.  However, Poseidon finds
out that Odysseus is back at sea and creates more trouble for
him.