In the book The View from Saturday, what brought Nadia's Grandfather and Margaret Draper together?

Nadia says that "turtles had brought Grandpa and Margaret together".

The year after his wif, Bubbe Frieda died, Nadia's Grandpa Izzy sold the house that they had lived in together and moved to Century Village.  Like many of the Village's residents, he soon got in the habit of going for a walk every morning, and one spring morning he noticed a blond, "pleasingly plump" woman returning about the same time he was leaving.  Grandpa began to start out on his walk earlier, and one day he introduced himself and asked the woman if she would like to walk with him.  She replied by "inviting him to join her on her turtle walk.  Grandpa Izzy accepted the counter-invitation, even though he was not quite clear about what a "turtle walk" was.

Margaret Draper is very interested in the life cycle of the sea turtle.  It is the female turtles' habit to come out of the ocean and lay their eggs in holes they have dug on the shore up and down the Florida coastline.  They then return to the sea and do not come back for two or three years, when they are ready to lay eggs again.  In the meantime, the eggs hatch.  Hatching season is from about the first of May until Halloween.  If the eggs have been laid in an unsafe location, the baby turtles will die.  Margaret Draper is a member of a "turtle patrol", concerned individuals who walk assigned stretches of the beach from May through October, keeping an eye out for newly hatched turtles who might be in distress.  People who have been approved by the Department of Environmental Protection are allowed to move the nests to safer locations.  Active in this conservation movement herself, Margaret invites Grandpa to join her in saving the turtles.  Thus, "turtles (bring) Grandpa and Margaret together" (Chapter 2).