In general, hatches should be kept secured closed at sea.
However, a hatch (other than one referred to in Section 5.2.2) which
is to be open at sea for lengthy periods should be:-
-
.1 kept as small as practicable, but never more
than 1m2 in plane area at the top of the coaming;
-
.2 located on the centre line of the vessel or
as close thereto as practicable;
-
.3 fitted such that the access opening is at least
300mm above the top of the adjacent weather deck at side.