well at night the chances are smaller, but at a hotel pool people will still pass by. So its not that simple. Maybe at a beach at 2 in the morning its something else.
By the way A jid and goy is not the same. A wife is not "nichshel" a goy, but a yid she is. Thats the 1 issue. The second issue is, that there is a problem of "mokoim sheminhag lechasois" (hair is a ervo and she for sure has to cover up) and then its not znius. So I asked a poisek if there might be a heter, since at the beach with only goyim a one piece bathing suit is more then normal. So maybe that takes care of the issue of "mokoim sheminhag lechasois" He is looking into it, if one can be matir. Ask your own Rabbi...