przewrócić się dnem do góry in English:

Optimists capsize easily.

if a boat capsizes, or if you capsize it, it turns over in the water

If I don't get down there right now it 's gonna capsize!

The boat had too many people onboard so it capsized.

What would you have done if the boat had capsized?

reportedly survived in an air pocket inside the MV Nyerere ferry, which capsized near Ukara island