In an urban fantasy type world, how exactly would public transit work for merfolk?
Situation A: The merfolk are living in a big cross-species city that also has humanoids. For purposes of this question, I'm assuming they have specialized buses. How exactly would these buses work, and what would they look like?
Situation B: These merfolk live in the midway point of the ocean. Not the shallow coral reefs, but not the lightless abyss either. What could they use for their public transit, keeping in mind that they don't really have the ability to use things such as wheels and electricity. The bus would also span several 'levels' as there are no particular streets.
EDIT: The shallow merfolk can avoid water for about a week before drying out, so that isn't an issue. They are based off of dolphins, being able to breathe out of water and being able to hold their breath for 2 hours, though I am considering making it longer. They have no way of getting legs and currently, I have no real plans to put them in wheelchairs, though it is a possibility.
The city either has canals beside the sidewalks or tubes underneath the pathways, though I am leaning towards the former. The public transit needs to be able to get them to the merfolk-oriented areas and the public areas (such as city hall and a multitude of stores).
I'm assuming the bus could drop them off in a canal/tube entrance by the stops.