Highfield Ocean Master 350 Owner's Manual page 16

d) The boat's stability is affected by adding to the weight of the superstructure.
e) When under way, it is advisable to shut the hatches, lockers and doors to minimize the risk of flooding.
f) The boat's stability can be reduced when towing a boat or when using a davit or boom to lift a heavy load.
g) Air chambers shall not be punctured.
h) Breaking waves are a serious stability hazard.
Warning
Always adjust the speed and heading of your boat according to the sea conditions.
All of the watertight hatches and bilge drain plug must remain closed when at sea.