My understanding is that women sailed on sail powered ships (caravels) such as the Mayflower. On the other hand, I have read few accounts of women sailing on earlier, oar-driven ships such as triremes or galleys. (OK, Cleopatra did at the Battle of Actium, but she was Cleopatra.)
When did women start sailing as passengers on ships in meaningful numbers? Was it when wind-driven ships meant that it was no longer necessary for everyone to row their own weight, or was there an earlier dividing line?
This question relates to ocean-going vessels, and not ships on rivers or near the shore. (In the game, "Civilization," a trireme (rowed boat) has a 50-50 chance of sinking if not adjacent to the shore. Admittedly, this is a game, but it illustrates a point that rowed vessels might not be considered safe enough for women on oceans.)
When I refer to "women" on ocean-going ships, I do not include female slaves (who had no choice in the matter). And women who were the "wives of governors" would be included under the heading of "Cleopatra." So "women" in this context would refer to "middle class" women (neither rulers nor slaves) travelling on their own account.