Final answer:
The primary conflict in 'Greyling' is the internal and emotional struggle of the protagonist's adoptive parents, as they contend with the inevitability of their selkie son's return to the sea.
Step-by-step explanation:
The main conflict in Greyling is an internal struggle that the main characters, a fisherman and his wife, face when dealing with their adopted selkie son's longing for the sea. The couple has to come to terms with the nature of their son and the realization that they cannot keep him from his true home, the ocean. Moreover, they cope with the emotional turmoil of letting him go, which presents both an internal conflict within themselves and an emotional struggle relating to their environment and circumstances.