No.
No oxygen.
Yes, it is possible for an eel to drown. Unlike other fish, its gills are unable to obtain enough oxygen to survive. It therefore has to surface for oxygen periodically.
If the water does not contain enough oxygen, yes.
plants drown because their roots have mitochrondia (in them which supply the plant with energy to survive) that need air which they take from the air spaces in the soil. If there are no air spaces the plant cannot obtain oxygen and they 'drown'.
Actually, it is about the same thing, lack of oxygen.
Fish use their gills to extract oxygen from the water, the same way that a human uses their lungs to extract oxygen from the air. The difference is that gills are supposed to be underwater, so of course water doesn't prevent them from working, and therefore they can't drown.
Mermaids could be drowned maliciously. Drowning is just suffocation in water. In stories, mermaids breathe air like us, or water like a fish. Fish gills take dissolved oxygen from water, so if there is no oxygen in the water, the fish suffocate. It seems likely then that putting a mermaid in a sealed tank with no vapour exchange to oxygenate the water would cause the mermaid to use up all the available oxygen in the water. She would then suffocate, or drown.
Yes you can but only by draining all the oxygen. If the bedbug is in a room, and the oxygen is removed, this will also suffocate any other animals - and people.
Yes a fish can drown if they are kept in water completely devoid of oxygen and they are unable to get to the surface to desperately gasp for their lives. Fish breathe oxygen, not water, they filter oxygen out the water through their gills. If the water has no oxygen, they effectively suffocate.
Yes land snails breathe air. so they can drown in water. Sea snails and fresh water snails breathe oxygen derived from water using gills so they can drown in air. I guess that the rate that they expire at is quite slow since their metabolism would be very slow.
In a way, yes, if there is not enough oxygen getting to it, and there is an excess of non-vital fluids in your bloodstream, your brain could be considered as drowning. Alternatively, if you are inhaling gas that is not oxygen, or another fluid that is not oxygen, your brain could be considered as drowning.
Kind of. Fish need to breathe water to get oxygen. If they can't breathe, or if the water has too little oxygen dissolved in it, the fish will die from lack of oxygen (I would say suffocate; you may say drown).