I disagree.

Out on open deck, I've found on several cruises (number seven comes up to two weeks) that the ships have been amazingly quiet.  Obviously you're not gonna be trying inside a steel-plate enclosed cabin/stateroom/inside lounge, but be exposed outdoors... with no problem using a decent hand-held such as the Tecsun PL-380.

The Big Challenge is avoiding close range lighting (so seeing can be interesting at night if you're trying to take notes) and sheltering from wind for comfort, which can be a nuisance even in warmer climes.

Walt Salmaniw from Victoria, BC has proved all this on several occasions... including stuff I experienced during late evenings north of NZ heading from Auckland to Tonga and beyond.

The 380 off the coast of South Africa/Namibia provided outstanding reception up into the Mediterranean and Middle East, along with what at the time was a mystery in Chinese on 1098... which turned out to be CNR 11's 1000kW tx from Golmud.  It helps that South Africa isn't exactly a big AM user.

Identifying what you're hearing is going to be interesting but, hey, that keeps the grey cells alive.  Explaining to other passengers is the same as on dry land -- crew members can be inquisitive... late-night visits to a higher, exposed deck can be checked! 

And even mid-afternoon snoozing with an extended antenna poking through the deck railing earned me a visit from a Senior Officer to prove I wuzn't 'fishing' over the side!  I kid you not... he admitted his wife (so that's how Senior he was) had reported me.

You'll hear tons... enjoy it all.

TD