The Blue Hole

Briefly about The Blue Hole manga:

Yamato wanted to go exploring... deep underwater. But where were all the dinosaurs? And what about humans? Join Yamato and his friends as they discover a gateway in time and space, and find themselves transported back to the age of the dinosaurs! A science fiction manga series that blends humor with action and adventure as it follows young Yamato on his journey through time. Collects episodes 1-6 of the series.