Australia regained the Ashes on Tuesday after recording a 150-run win over England in the third Test at the WACA Ground.
A weary-looking Watson fronted the media on Wednesday morning after spending the previous night celebrating with his teammates at a party thrown by Shane Warne.
Watson described the Ashes triumph as the most special thing he's experienced during his playing career.
"It's still trying to sink in more than anything," Watson said.
"It probably won't for a little while.
"Even going into day five of this Test match, I was just trying to put it in the back of my mind thinking about winning the Ashes, because it was certainly something that's been so important to all who's been involved in the Australian team.
"To be able to have the Ashes urn back - certainly we had a great night last night celebrating.
"We had a lot of fun."
Australia have already set their sights on recording a 5-0 series sweep after dominating England in Brisbane, Adelaide and Perth.
England captain Alastair Cook says his team is devastated to relinquish the urn in such limp fashion.
But he has vowed to fight back in the remaining two Tests, starting with the Boxing Day clash at the MCG.