Here we can see the upper gun deck of HMS Victory (underneath her 'little boats') as it appeared in circa 1794:
Along both sides, a single row of 12-pounder cannons was present, together with the gun crews that operated them. The gun crews themselves, would both 'live and sleep' in the spaces between the cannons (especially of lower gun decks). The other gun decks were similar (in terms of layout) - although the middle gun deck was equipped with 24-pounder cannons, and the lower gun deck was equipped with 32-pounder cannons. The heavier calibre cannons were located closer to the waterline - to improve the stability of HMS Victory. This was a lesson 'learned the hard way' as ships of the line that were 'too top heavy' were notoriously unstable (such as the Mary Rose). In any case, the armament of HMS Victory 'tended to vary' both depending upon the century and 'which admiral/captain' was in command. For example, some admirals preferred the 42-pounder cannon to the 32-pounder cannon. Whilst the 42-pounder cannon featured more 'hitting power', it also featured a slower 'loading time' - because the cannonball weighed more, and was 'harder to lift' for the gun crews. The material used to construct the cannons also varied 'depending upon the century' - with early cannons being made of brass, and later cannons being made of iron (which were also equipped with 'more modern' firing mechanisms).
The early World War Two modifications of HMS Hood, resulted in Hood's 'boat deck' (also called her 'shelter deck') being outfitted with seven 4 inch 'twin barrelled' anti-aircraft guns:
This was something of an 'austere makeover' that aimed to increase Hood's anti-aircraft capabilities. To 'make space' for installing these guns, all of Hood's single barrelled 4 inch anti-aircraft and 5.5 inch naval guns 'were removed' - although facilities (such as their magazines and 'shell supply lines') were enhanced to support her new guns. These modifications were carried out 'more for speed' than for robustness reasons - as the entire 'boat deck' could really be considered as a target for incoming shells! This issue was further compounded, by the fact that 'ready use' ammunition lockers were installed 'next to and near' each anti-aircraft gun mount. During the Battle of the Denmark Strait, a boat deck fire 'wreaked havoc' amongst the ammunition that was stored in these.
HMS Hood was an Empire Ship that sailed the world. As such, her upper decks were an interesting mix, of both peacetime and wartime:
For me, the peacetime is represented by the variety of smaller boats that she carried on-board. I believe that these were used when she was in port, or when she had anchored off some tropical island, for some rest and relaxation (for her sailors). Yet, she was still a warship, with the armament to match! Here we can see: a 5.5 inch naval gun (lower left), a 4 inch high angle anti-aircraft gun (middle-bottom), and a quadruple 0.5 inch anti-aircraft gun (middle-bottom right). Now, I've heard it said, that sailors don't have a fear of heights! Hood's main mast, would appear to test this theory - with the mast's ladders being used to gain access, to both lookout posts, and wireless radio equipment. The long horizontal boom, that stems from the base of the main mast, is the main derrick, which was 65 feet long! I believe this was used, to lift both the smaller boats, and other heavy equipment (such as ammunition crates).