Ah my bad. xD
I thought we were talking about if Akainu turned himself into magma during the fight.
zetruz was saying if he turns into magma, he'd not be affected by air-removal, but as far as we know, he still needs to breathe even if he can't be touched by attacks.
No, he doesn't. He turns into actual magma. Hitting the magma won't affect Akainu, because it isn't his actual body. Striking the lava with a hammer won't hurt Akainu. (Unless you use CoA, which actually materializes his body, thus materializing his human cells.) Luffy, however, is a rubberman. That is, he is still a man. His cells may be made out of rubber, but he still bleeds. His body still functions normally. When Akainu is in his magma form, the magma does not at all act like a human body. Luffy's does, with added stretchiness.
That's a fair point; I should've said "Akainu might not need to breathe, because he can turn into magma".
But he still talks, thinks, sees, hears etc. He uses certain anatomy, still. Some Logia are fairly dependent on their natural physical form for movement etc. So it's hard to call a line on where human ends and element begins.