The ferry-boat rocked like a sieve and was about to capsize.
When a boat is topheavy or its center of gravity is too high, the boat is liable to capsize.
Suppose the great monster did come up and capsize them—they were ever so far from land.
“Capsize her and let her drift,” said the leader of the party.
Jack helped me in and then I balanced his effort so as not to capsize ...