Iacisrmma – Rav Moshe Feinstein has a teshuva about this. I am not sure if I ever saw it inside or only heard it quoted, and in any case it was a long time ago, so anyone who wants to know exactly what he said should look it up themselves (or ask DY to find it for you – he’s good at that).
But, I am pretty sure that he says that if you need to ride the bus for parnassah, and there is no other way to get to work, and riding the bus involves sitting next to someone untzniusly dressed, then you are allowed to.
I believe this is a clear-cut halacha based on Chazal. If someone has to pass by people who are untzniusly dressed, he is allowed to, but if he could have found another way to go, he is called a rasha.
As far as I know this halacha applies to all of the above situations mentioned – cruises, hotels, walking down the streets of Manhattan, and even entering a bank where the tellers don’t dress tzniusly if one has the option of using the ATM or going to another bank where the tellers wear uniforms.
Every person has to figure out for himself if he really has another option or not. Sometimes he doesn’t and sometimes he does.
Sometimes, there really is another way to go, and the person does not realize it, but if he thought harder about it, he would realize this. I have a story about that, but I don’t have time now. Will try to post later, b”n.