I don't really see people whimsically genetically modifying themselves. Cosmetic surgery is one thing, but our basic form is a humongous part of our identity. I would suspect that weird people, or people who have had their right to chose taken away, would be the majority of the genetically modified minority. 

It seems way more likely that people would find some way to settle on top of or in an ocean than it would be for them to go "Ala-Kazam! Little Mermaid tiem."