(Found) Sci-fi book written before 1982 about time travel and battleships

[Dyantier]

My dad has always told me about a book he read when he was 17. That was in 1982, so it has to have been written before that. It was about an apocalyptic future where the world was covered in water and the land was all mush. Warfare was fought with battleships that were apprehended by time traveling back to when such ships were made and stealing them. He remembers one part in it where a guy on a boat suddenly sees a gill-man attach something device to his boat and he is transported to

Tl;Dr:
Written before 1982.
Watery apocalypse.
Mush land.
Battleships (that were stolen with time travel).
Gill-men?

Any help would be appreciated!

 

[Peter V]

It has some similarities to the Winged Man by A E Van Vogt. Certainly a submarine is transported to a future where the world is covered in water

 

[Dyantier]

It has some similarities to the Winged Man by A E Van Vogt. Certainly a submarine is transported to a future where the world is covered in water

Yes! That’s it! My dad confirmed that was the book he was looking for. He’s already ordered it from eBay so he can finish reading it (he never did finish it back in the day). Thank you so much for your help!

 

[Peter V]

Yes! That’s it! My dad confirmed that was the book he was looking for. He’s already ordered it from eBay so he can finish reading it (he never did finish it back in the day). Thank you so much for your help!

Glad to be of service