What to wear at night- how casual is smart casual?

Hi, i am looking for some advice, we are sailing on the Britannia in Jan 2018.

My boyfriend was reading through the dress code and is wanting to wear long linen trousers on some of the non formal nights in the main resturants (non buffet) but is unsure what to wear on his feet as it sounds like the only things left are formal shoes.

When it says no trainers does that mean no sports style trainers but smart deck style canvas “trainers” are allowed? Or is it all a big no no. Help please - We are used to very casual wear on NCL. Thanks :D

My husband always wears boat shoes on the casual evenings. The dress code does state no trainers but on most of the P&O ship's that we have been on there have been men wearing black trainers that at a glance are not obviously trainers ( they don't get down on the floor and inspect anyone's shoes ).

Dark trainers or walking style trainer shoes are probably ok - fancy white or neon "nikes" will probably stand out for the wrong reasons....I usually take black shoes, deck shoes for casual nights and trainers/ walking trainers for day wear.

My husband also wears boat or deck shoes to smart casual evenings, or whatever they're called now. He doesn't tend to wear trainers during the day anyway but I would think dark/black trainers wouldn't raise any eyebrows but as has been said, glistening white ones might.