estimating range and rough sea // wrong target?

[Tozzifan]

hi,
playing historical settings I'm finding quite hard to estimate correct range with stadimeter, as the target view bobbles due to waves motion, meanwhile the watch officer seems not to suffer any problems in determining range

do I miss anything to deal with the range acquisition procedure in rough sea?
does perhaps the officer use a MIL-DOT like (range determining grid in carabine shooting with optical scopes) acquisition system? ... in that case that ranging trick should be appliable to UZO and periscopes as well, isn't it? (and maybe it would relieve the captain from stadimeter nightmare... nonetheless, if there was a stadimeter, that was because it was useful )

thanks

BTW (second question): on patrol on 09-12-1939 I sank a couple of vessel docked into a polish enemy harbour (red labels, polish flags), but the patrol report catalogued that tonnage as axis' .... bug or my misunderstanding of the rules of engagement?