@littlek,
container-ships are in and out of harbours very quickly now - they don't wait for any lost passengers !
often the port of final destination is changed - depending on freight - so your return flight ticket may be useless.
NO STABILERS ! - lots of rolling and pitching while crossing the atlantic !
adventure channel has shown some interesting docus ( michael palin ) - check with your library .
and allow plenty of time in case of delay - be VERY flexible .
and have good sealegs and a sturdy tummy .