Frozen in time means unchanged over a long period: an Amish town, perhaps, where religious beliefs do not permit them to take up the modern conveniences of American life. (They still drive horse-drawn carts and make their furniture with hand tools).
Since I‘ve never heard the "the sea has no fences" as a coined phrase, I googled it. In the only site I found, the phrase appears under "metaphors". check it out In this case, I don't think that the meaning is too complicated, isn't it?