What animal is a fast swimmer and lumberjack?

That's a tricky one! There isn't an animal that is both a fast swimmer *and* a lumberjack.

* Fast swimmers are usually aquatic animals like dolphins, sharks, or fish.

* Lumberjacks are humans who cut down trees.

Perhaps you're thinking of a beaver, which is a skilled swimmer and also known for building dams and lodges with wood. But they don't actually cut down trees like lumberjacks. They gnaw on them with their large teeth to get the wood they need.