What happened to Odysseus at sea?
Quite a bit! After he blinds Polyphemus, the Cyclops son of Poseidon, lord of the seas, his journey by sea becomes much more difficult. For example, at one point, Aeolus, the keeper of the winds, gives Odysseus a bag containing all of the winds except the one Odysseus needs to blow him back to Ithaca. However, with home in sight, Odysseus falls asleep and his men open the bag, thinking it might contain some treasure. The winds escape, and their ship is blown all the way back to Aeolia. Aeolus, understanding that some powerful god is working against Odysseus, will not offer him help again.
In another instance, when Odysseus is swimming, alone, in the sea, his ship having sunk, Poseidon sends a mighty storm, attempting to drown the hero. Odysseus grips a giant rock, but the force of the water is so strong that he leaves pieces of skin stuck to the rock when he is ripped off of it. Ino gives him an immortal veil, and this helps to save his life and allow him to reach Phaeacia.