The daily life of a mermaid is to look at flowers, eat grass, eat fish and confuse humans, and then the most important thing is to worship His Highness the mermaid.
His daily life as a mermaid is to be worshiped by mermaids, capture the sister who fell in love with the prince, educate the mermaid who eloped with humans, and find the stolen heart of the ocean.
Oh, and probably falling in love.