He may own the shoreline in front of his house but he certainly doesn't own the lake! You need to let your neighbor know that you'll go swimming in the lake anytime you feel like it and if he doesn't like it tell him to go jump in that Lake. :)
We live near the lake and our neighbor lives closer to it and built a dock on it and said we can’t swim in the water cause he don’t want us to. Does he own the lake or a small part of it?
No! The lake is a natural resource and no one owns it. You
have the right to swim in it whenever you want to and your neighbour cannot
stop you from doing so. J
Even if he has built a dock on it, he does not become its owner.
Good luck!
Doubt if your neighbor owns the lake. You may not be able to use the dock though.
Ask them to produce the documents showing what they own.