Cogs receive the same 'Lost at Sea' debuff text and warning notification as other coastal ships do, despite their 'Navigator' ability stating they will not be destroyed, only damaged (and I have verified they are only damaged).

Send Cogs into deepwater tiles, go to next turn.

 5/5

'Navigator' ships shouldn't have the same warning as Triremes/coastal ships, as they aren't destroyed contrary to the warnings, only damaged. Either that or the warning itself should be altered to clarify damaged and/or destroyed.