3 years ago I sailed my 43 year old NC33 ZARZUELA across the Channel from Portsmouth to St. Vaast in near gale force Easterly winds, engine running to ensure we made the tide to enter St. Vaast. One mile off at 0400 the engine stopped on a lee shore. French signal station helped issue a Pan Pan and we were rescued by the SNSM Lifeboat who towed us into the Marina.
ZARZUELA has fuel tank air vents below the maindeck level and the severe rolling during the crossing dipped them underwater to suck in the water (20 ltrs. of water in each tank!).
I was advised to have the vents lifted above deck level, as some boats have, but due to costs have not done so yet.