In dreams, transportation like cars and buses (and I assume boats would count) are supposed to be a symbol of either change, or the idea that life is a journey.

I did a google search, and dreaming about the ocean can have a couple different meanings. One is that any water reflects your mood (so if the water is rough, that might mean you're angry, but quiet water would mean you're calm). Another is that it's a symbol of your birth, your mother, or just a general sense of where you come from.

I know that money is supposed to stand for self-confidence, so losing your wallet might mean that you feel like you're losing confidence in yourself. But I found out that wallets sometimes also mean your identity in general, so it also could mean that you feel like your personality or your values have changed. It probably is meaningful that you got your wallet back in the end of the dream, though.

That sense that people (the boatman and your sister) are trying to help you, but that you don't seem to want help probably means something, but I'm not sure what, unless it's that you literally feel that way about something in your life.

Put it all together, and there are lots of different ways to interpret this, but maybe the simplest is that you feel like you're going through a lot of changes in your life, and you're worried that they're changing who you are as a person.