I think it's safe to say that people do see you (if you let them), do know that you are in the water (again if you let them and often even when you don’t) and that while their lives seem to be all about sunshine and fun - none of us ever really know what is going on up the beach (behind those facades or closed doors) i.e. slow burning skin, sand in your bathing suit, flies in the picnic etc.
What I mean is that other people's lives often look better than ours and we feel they can’t see us - but most of the time neither of these things is true.
There is no shame in not coping. It's not that you can't, its that you haven't found the skills that work best for you - yet.
Share your load. Reach out, or let them in. Give people parameters to work with if you want a certain kind of help.