Most charts are now produced with Metres for the soundings. Cables, Fathoms, (Leagues!) are still in general use. The more modern Echo Sounders can switch their readouts to either Metres or Imperial (feet, fathoms).
I have to disagree with you Wiley on your assessment of the seaplane being damaged from the main armanent. I have stood out in the open, and abaft of the forward 4.5 inch guns at my action station and only felt a slight pressure wave when they were fired. I doubt, therefore, having a slightly larger calibre of 6 inches would produce a signifcantly larger shock/pressure wave. In fact you would in more danger of being hit by the turret which often turned without warning. Hence the reason for the decks around the guns to be cleared of personnel when firing.