Not Waving, but Drowning

The title alone, before reading the poem makes me think of a drowning person desperatly flailing and someone not recognizing it is a cry for help. As I read the poem i realize that the man is dying and they are already passing him as off as dead. They say he is " moaning" but call him dead. The last line:
"I was much too far out all my ife
And not waving but drowning"
That line , to me, means that he never got paid any attention. He was never noticed no matter how he acted or what he did. The remark about larking, or harmless pranks, shows that he was trying to get attention. This poem makes me think of a very lonely person with a sad life.
The line "I was much further out than you noticed" is saying that no one took the time to realize he needed help.