The crewmen fell into the sea as the ship was rocked by a sunken rock.
The crewmen fell in the sea as the ship was rocked by a sunken rock.
The crewmen fell to the sea as the ship was rocked by a sunken rock.
I usually use "fall into", because it sounds better, but I am wondering if these alternative sentences have a similar meaning and are grammatical? What are the differences in meaning though?