Short and plainly worded, the poem is about reaching for the wrong cure. The speaker describes someone taking more pills than they need, and then compares that to diving into a lake without knowing how to swim. Both images show a person moving toward danger while hoping for relief.
The tone is quietly weary. The speaker calls the situation "a little bit sad, and a little bit ironic," which sounds almost casual, as if the sadness is too familiar to shout about. That understatement is what makes it unsettling. The word "tonic" suggests that life leaves people feeling they need a fix, and the last two lines show what that fix becomes: a little more alcohol, a little more drugs. The repeated "a little more" makes the habit sound small and harmless, even though it keeps growing. The irony is that "just to be happy again" is exactly what the poem suggests is slipping further away. The mood is bleak but gentle, more sorrowful than accusing.