Australia's top swimming coach has defended national team captain Grant Hackett's perceived weighty physique after he failed to qualify for the 10km race at the Beijing Games.

Hackett, who is the captain of the Australian swimming squad, lost his bid to race in the inaugural 10km Olympic event in August after he finished 15th and was later disqualified at a Seville qualifier on Sunday.

Images of the swimmer emerging from the water show a solid belly bulging over the top of his skin-tight swimming costume, prompting Sydney's Daily Telegraph to run the headline: "Has Hackett got the guts to race in Beijing?"

But head coach Alan Thompson jumped to defend the two-time Olympic 1500m champion.

"I think everyone has been a victim of a non-flattering photo at some stage of their life and that is what the context is there," he said.

"Grant has been training his heart out over there for the whole time. I think the focus on that takes away from what should be really focused upon."

Hackett, 27, who last year struggled with form, was also defended by his Melbourne-based coach Ian Pope who said that distance swimmers were not normally as toned as those racing shorter distances.

"The sprinters are very defined in their physique, you generally find the distance swimmers do carry a bit more, whether that is because of their training I am not sure," he said.

"One of the things I have observed over the past 12 months are that Grant's skin-folds are the lowest they have ever been and his weight is the lowest so there is no problem there."

Pope said Hackett's skin-tight ankle-to-hip trucks may be to blame.

"Sometimes those tight bathers, when they put the strap on the top, it is an elastic thing and it has to be very tight so that no water gets in," he said.

Hackett finished 15th in the 10km race but was disqualified for obstructing an opponent.

Pope said Hackett's elimination would allow him to concentrate on his 1500m and 400m races.

"Grant always has been such a focused athlete and that will just keep his focus in the zone a little bit more now," he said.

AFP