English to Polish Law/Patents Ships, Sailing, Maritime

Wiem, że 'roll' to kołysanie boczne. Ale jak odnieść się do pojedyńczego wystąpienia takiego zdarzenia - kołyśnięcie nie brzmi zbyt profesjonalnie.

Kontekst:

At the end of the roll, the valve is closed, this traps the water in the tank and it is then lifted during the next half roll, at the end of which the valve is opened briefly.