How do you grow a mermaid tail because you hate living on land you want to be a mermaid?

Answer 1

You cannot. Mermaids are not real. Speak to your parents or teachers.

However for the sake of possible possibilities of what seems impossible today.

The future might hold an answer.

The best choice would probably be to actually research genes. Both your own genes and the genes of the fish you would like to have the tail of. I would consider the Merlin fish a great choice. It provides high speed and stamina.

After you have finished your gene research you should have found out which genes that can be activated in order for entire limbs to grow out if they are cut off. (some reptiles and most crabs can actually do this.)

You must also have isolated the genes that makes the Merlin fish-tale.

Now for the tricky part:

Chop off your legs, possibly remove them surgically by taking them out of the socket would be a better choice as when the fishtail later grows out it will be a more proper part of you. This can be done under anaesthetic and does not always hurt so much (until after).

Via gene manipulation and gene therapy you alter your genes so that you insert gene information for growing a tail instead of limbs, and then you activate the regrowth gene. Stem cells from the Merlin would be most useful.

Be aware that it might itch a bit as the new tail grows out. This process may take up to a year before the tail is big enough for proper use as in swimming. Don't worry though. As time passes it will grow bigger and stronger.

It is very important that you do not scratch your scales off due to the itching.

A tail without scales is not a very healthy tail.

After you have a proper tail you might want to consider gene therapy for growing gills, but this is a different story.

I never dispute the possible possibility of what seems impossible as long as it is not an impossible impossibility with no possible possibilities to be possibly possible.