After her return in March, Bass and Flinders, being free again, lost no time in fitting out for a second cruise.

Their object this time was to search for a large river, said to fall into the sea to the south of Botany Bay, which was not marked on Cook's chart.

As before, the crew consisted only of themselves and the boy.
It has always been believed that the boat in which this second cruise was made, was the same Tom Thumb as that which carried the two young explorers to George's River; indeed, Flinders himself, in his Voyage to Terra Australis, Volume 1, page 97, says that "Mr.Bass and myself went again in Tom Thumb." But in his unpublished Journal there is a passage that suggests a doubt as to whether, when he wrote his book, over a decade later, he had not forgotten that a second boat was obtained for the second adventure.

He may not have considered the circumstance important enough to mention.

At all events in the Journal, he writes: "As Tom Thumb had performed so well before, the same boat's crew had little hesitation in embarking in another boat of nearly the same size, which had been since built at Port Jackson." There was, it is evident, a second boat, no larger than the first, or that fact would have been mentioned, and she was also known as the Tom Thumb.