Like this, only better
Polly Ann is the hired wherry on board which the story of Peter Duck was written by the Swallows, Amazons and Captain Flint during the 1930 Christmas holidays in Norfolk (TOS reprinted in CFT10).
Is she Arrow of Norwich?
In 'Their Own Story', Peter Duck appears as a hired wherryman who seems to come with the hired ship, and he could well be the owner. Since in this early manuscript Arthur Ransome flips between the names Gibber and Jacko for Roger's monkey, he might well have conceived Polly Ann as Mr Duck's "day job" ship, called Arrow of Norwich in the final published Peter Duck.
The other Polly Ann
Polly Ann is also the name of a racing yacht moored off Rio when the elder Swallows and the Amazons crossed the Lake in fog in Swallowdale (SD32).