No, you should never go swimming with contact lenses in. Tap water is risky, while lakes, streams, ponds, the ocean, and even chlorinated swimming pools are teeming with life, none of which you want between your contact lenses and your cornea. In the event you get thrown from a boat and end up in the 'drink', get your contact lenses out of your eyes as soon as you are safe. Don't finish a 3-hour cruise and then take them out back at the hotel, take them out as soon as possible. Plan ahead, have your lens case handy, and spares in the hotel room (or wherever you are).