Complex sentence: ORP "Wilk" was a 980 ton (surfaced)/1,259 ton (submerged) French-built mine-laying submarine, the lead boat of her class, which saw service in the Polish Navy from 1931 to 1951.
Split into simpler sentences: ORP "Wilk" was the lead boat of her class of mine-laying submarines of the Polish Navy. The ship saw service in the Polish Navy from 1931 to 1951.