This song is about love. He is in love with someone who: (A) Doesn't love him back, or (B) Doesn't know he exists. It's like there is no difference between being where he is and being at the bottom of the sea.
"I'm barely there for you" refers to the lack of interest by "her". He's not important/noticed.
Continuing with the idea that he's at the bottom of the sea, "the air and light", which are things someone would obviously need if they were at the bottom of the sea are not necessary in his mind. All that matters is her.
This song is about love. He is in love with someone who: (A) Doesn't love him back, or (B) Doesn't know he exists. It's like there is no difference between being where he is and being at the bottom of the sea.
"I'm barely there for you" refers to the lack of interest by "her". He's not important/noticed.
Continuing with the idea that he's at the bottom of the sea, "the air and light", which are things someone would obviously need if they were at the bottom of the sea are not necessary in his mind. All that matters is her.