Salieron a comer y luego fueron a nadar.
Salieron a comer y después fueron a nadar.
Both of these translate to: They went out for lunch and then went for a swim.
In English, there are so many words that I frequently use interchangeably. I'll randomly interchange such words for no reason in particular, but still it sounds natural.
So ultimately, I'm asking if it sounds like natural Spanish to interchange 'luego' and 'despues'.