The mouth of the Vistula River into the Baltic Sea can be visited on both sides of the river - on the right side, in Mikoszewo, or on its other bank in Gdańsk-Świbno, on Sobieszewska Island. IN
Supposedly the same river, on one side a forest, on the other side, there is seemingly no difference, but... walking in Mikoszewo we will not reach the very "junction" of the river and the sea. Here, at the end of the coastal path, behind a metal fence, there is a concrete seafront inaccessible to tourists, which is part of a nature reserve and a resting place for gray seals.
This place is often guarded by guards, so even if someone wants to go beyond the "no entry" line, they may face a fine. On the other side, it is a bit different, even though it is the same nature reserve (Mewia Łacha), but it is more accessible to visitors, there are viewing points here, and, most interestingly, you can get really close to the water.