If constructed, I don't know whether the ancient vessels would ever be able to found if they were constructed out of biodegradable materials?
In terms of the physical and mental capacity required, I recall discussions about dinosaurs having limbs and digits with the needed movement and dexterity requirements.
There is also a comparison of modern dinosaurs to ancient dinosaurs for such things as speech and reasoning abilities to support how they could have had a basic intellectual capacity for such tasks.
The span of time since the referenced era is so vast that, as has been stated, anything could have occurred and that all points made in this thread should remain a consideration as to what did occur.