On December 3rd her westward course was resumed.

From this time forth Bass and Flinders were in constant expectancy of passing through the strait into the open ocean.
The northern trend of the coast for a time aroused apprehensions that there was no strait after all, and that the northern shore of Van Diemen's Land might be connected with the coast beyond Westernport.

The water was also discoloured, and this led Flinders to think that they might be approaching the head of a bay or gulf.

But on December 7th the vigilant commander made an observation of the set of the tide, from which he drew an "interesting deduction." "The tide had been running from the eastward all the afternoon," wrote Flinders, "and, contrary to expectation, we found it to be near low water by the shore; the flood therefore came from the west, and not from the eastward, as at Furneaux' Isles.

This we considered to be a strong proof, not only of the real existence of a passage betwixt this land and New South Wales, but also that the entrance into the southern Indian Ocean could not be far distant." On the following day the deduction was confirmed.