Mr. and Mrs. Carnahan live in the Lake View Naturist Park. Mark Robins helps them fix their car. Both are old, and pay a "very young, very voluptuous, naked lady" to take care of them. They are in wheelchairs, and friends of Beth Phillips.
Mrs. Carnahan has been showing Bonita Sharp how to play the violin, and planned to let Bonita play her on the boat trip. It's probably not the same woman, but there is not enough info to determine for sure.