Is there such a thing as a shell-less turtle?

There is no such thing as a turtle without a shell. The shell is a necessary part of anatomy that forms a protective barrier for the turtle's internal organs, since the turtle lacks independent bone structure on its abdomen.

Softshell turtles from the Trionychidae family and leatherback sea turtles have soft shells covered with skin rather than hard shells covered with bony plates. Both softshell and bony shell turtles have their rib cages, parts of their pelvises and their spines assimilated as part of their shell; to remove the shell would be to remove the skeletal protection that other animals take for granted.