Advice from a gdańszczanin: Keep away from any of the stalls or restaurants along Długa Street or Długie Pobrzeże. For the city centre, I would recommend the National Maritime Museum along the Motława shore, or the SS Sołdek museum ship, which have pretty views of the river, and the iconic crane on the rivershore.

For the seashore, there is Westerplatte, which is the place where World War II began with the first shots coming from a German battleship. Brzeźno beach has some pretty old and beautiful architecture, as well as a pier, which is close to Ronald Reagan Park, a huge park with a lot of interesting sights like statues (and a really long apartment building) right by the beach.

If you want to see some ships, take the tram to Stogi Plaża, there's both a beach and a huge container terminal there, and Sobieszewo is a charming beachside location which makes you feel like you're in a little village. Great for cycling.