I don't know much about cycling in Poland. From some of the roads I've been on, I might be better off catching a couple of trains instead
Well, you need a good map and some planning before such a trip. I hope you wouldn't like to go the shortest way (inhalating the exhaust gases from the cars on the motorways and generally risking your life/health). Trains are a good option on some stretches, but cycling through the National Parks (Woliński - with Polish bison, żubr, at Międzyzdroje, and Drawieński - with kayaking trails, if you really want to row, row, row your boat).
Gdynia's named after a river. Świnoujście looks like it's named after pigs.
No, "ujście" is the final part of a river (like delta, estuary, firth etc.) before entering a larger body of water (like another river, sea, ocean) and "Świna" (not "świni
a" is the name of the local river or more precisely strait. The Odra river estuary enters the Baltic Sea through 3 straits (which are sometimes consiedered 3 short rivers, 16-20 kms long) and Świna is one of them.