The script for grandad otas first story - choshi no taki
 
B

BT
Before the invention of cars, trains or even horses the fastest way to get from a to b was by swimming down a river.
Back then choshi river was your modern equivalent of the super highway connecting matsuyama to niihama. There were even traffic lights and pedestrian crossings. The falls itself was a kind of service area where people could take a break before conyinuing their journeys.
Everything was very well organised. Seats were prepared underneath the falls and when a swimmer came over the top they would land directly onto their chair to Chow down on a nice warm bowl of udon noodles. They also did udon deliveries by floating bowls directly to your home.
With the invention of your new fangled cars fewer customers came to the shop and it eventually closed down.
It's a shame really. It really was the safest means of transportation. Have you ever heard of a swimmers engine breaking down?

Back at the carehome

Potsu : well I've never heard anything so ludicrous.
Tajizawa : why did you need to go to matsuyama grandad?
Ota : oh just shopping or what have you.
Potsu : how did you bring shopping home without it getting wet?
Ota : I mainly bought matsuyama orange juice so it didn't matter.

A description of choshi falls true information, ending with "it has never nce  used as a super highway"