How Would Living Under the Sea Be?

I've thought about this often...especially if you are half human/ half fish. What would the sensations of life undersea be? Sound carries differently and further (for whales thousands of miles I'm told). Communication would be immensely different. Taste and smell are connected and seem to also carry far under the waves (a shark can smell from a very far distance). Seeing would have limitations not found above water. It is distorted by wave action as well as depth (it gets darker and bluer as you go down). Touch has a uniqueness to it. Certainly direct touch would differ, but also to consider is the lateral lines found on a fish body; this allows rhythms and vibrations in water to be sensed from a great distance. I have tried my best to get into character as a merman under water. I find the notion of understanding sensations as a Mer to be key in creating an understanding of how life undersea would be.