I think you may be on the right track.
Geological time implies very long term.
Water may be a code.
Dressed in dark clothes may mean something.
Sunglasses may signal something.
The words themself May send a coded signal.
That this appeared after Mueller finished with no additional indictments, seems too much a coincidence to me...
It looks to me like a signal that Comey is headed “ out across the water.” Wouldn’t be surprised if he is signaling to get out of the country.