Can Mermaids get Drunk?

I've been thinking a lot about mermaids lately, possibly on account of this weekend's upcoming Mermaid Parade in Coney Island. I don't think I'll actually make it to the parade, but I'll be there in spirit.

School Spirit!

I personally had a fine high school experience; very little trauma. But I bet if I'd been a merman, it'd have been a lot worse. Maybe it'd all be second nature to me if I actually had been a merman, but at the moment, I'm plagued with a LOT of questions:

Can merpeople drink alcohol? If they try to drink booze, does it get watered-down with sea salt? are their circulatory systems even comparable such that it's metabolized the same way?

Clearly mermaids can't smoke marijuana – it's not even clear to me that they have lungs. If you live most of your life underwater you must have gills, right? If they have both then that makes sense, otherwise why would they bask on rocks in the sun? (mermaids clearly bask on rocks in the sun, it's part of the profile).

Am I suffering from a critical misunderstanding here? Are mermaids and mermen severely sexually dimorphic, such that mermaids are sexy girl-fishes and mermen are ugly fish creatures human from the waist down? (A SICK INVERSION INDEED).

Or is that what all merpeople look like during puberty?

I don't know the answers to all these questions, but that's not going to stop me from making them up.