Complex sentence: Towards the beginning of the 17th century it was made navigable for large ships, and Swinemünde, which was founded on the site of Westswine in 1748, was fortified and received town privileges from King Frederick II of Prussia in 1765.
Split into simpler sentences: Towards the beginning of the 17th century it was made navigable for large ships. Swinemünde was founded on the site of Westswine in 1748, fortified, and received town privileges from King Frederick II of Prussia in 1765.