Australia's Olympic great Kieren Perkins is imploring swimmers Kyle Chalmers and Mack Horton to embrace being hunted at the Tokyo Games.

And Perkins says both Horton and Chalmers should treat expectation to defend their Olympic titles as a blessing, not a curse.

Chalmers in the 100m freestyle and Horton in the 400m freestyle will seek to to join a group of just six Australian swimmers to successfully defend Olympic crowns.

That group includes Perkins, the 1500m freestyle gold medallist at the 1992 Barcelona Olympics and four years later in Atlanta.

"The thing that you become really aware of ... is defending is very different to attacking the first time around - going from the hunter to the hunted," Perkins told AAP on Tuesday.

"The natural energy and aspiration and commitment that comes from trying really hard to get there the first time around is replaced when you're defending by that sense of, I guess, trying not to lose something.

"And it can be dangerous.

"Especially when you get into that little bit of a drift where all the little things that you used to do when you were starting out that you were committed to and would do whatever it took to try and achieve your best, that same intensity may not necessarily be there the second time around.

"The best advice I can give is just make sure you remember why you're there and what were the things that made you who you are in the first place.

"And if you stick with those - and don't let some of the new potential risk and consequence conversations that come with defence enter into your psyche - you have got a better chance."

Perkins is now Swimming Australia's president and on Tuesday oversaw the launch of Amazon Prime's coverage of next month's Olympic selection swimming trials in Adelaide.

Dawn Fraser (100m freestyle, 1956, 1960, 1964), Murray Rose (400m freestyle, 1956, 1960), David Theile (100m backstroke, 1956, 1960), Perkins (1500m freestyle, 1992, 1996), Grant Hackett (1500m freestyle, 2000, 2004) and Ian Thorpe (400m freestyle, 2000, 2004) are the only Australian swimmers to win as defending Olympic champions.

Perkins said media and public pressure can be draining "if you're susceptible to it".

"Honestly, your own expectation that you put on yourself far outstrips what anybody else can expect from you," Perkins said.

"From the media and the public's perspective, they are there and they certainly can play a part if you're susceptible to it.

"But actually, overwhelmingly, you tend to find that the support is quite positive.

"Even though there will be conjecture and there will be wonder about how you're going and can you do it ... generally the intent is really positive because people want to see you succeed.

"Focusing on that and not letting the negative stuff get in the way is key for any athletes ... especially for those that are defending."