While visiting Croatia, enjoy water, Adriatic Sea and islands.
You may meet jellyfish in the Baltic sea.
Mostly, they are completely not harmful to people.
But there is also a kind of sea jellies in the Baltic Sea that you should avoid, however it’s very unlikely to see it.
When I was a child, everyone was saying, thet “our” jellyfish are not harmful; it’s almost always the case; but it doesn’t mean 100%.
Nearby the town of Łeba, you can visit the nation park with sand dunes.
It’s a very nice and unique place in Poland.
The Baltic Sea (called by a few countries as “East Sea”) is a sea enclosed by 9 European countries: Denmark, Estonia, Finland, Latvia, Lithuania, Germany, Poland, Russia, and Sweden.
Summer in Poland should be hot, sunny with thunder storms from time to time. 😉
Well, it can be also rainy and not nice; difficult to predict…