is an onomatopoeia for light rain just as is for heavy rain. is a very common expression, so it definitely refers to rain. You can hear the sound here.
And I think we should simply parse that the subject of here is . In this context, is clearly about the rain, which is usually annoying. Of course nothing in the song suggests these people are on an unstable boat. is not a common expression at all, but I think this is a poetic way of describing some aspect of a rainfall, not a person. For example, they may be looking at the rain through a frosted glass.