A 1968 Caravan that was waterproof!!

[Dustydog]

If they could make them waterproof in 1968 what has gone wrong over the last 55 years??

View: https://youtu.be/v223HkqHJbo

 

[ProfJohnL]

Ah but it was only waterproof at the bottom!

 

[JTQ]

IMO they could make them water proof today, in fact they have way better products available to achieve this, its just "they" don't care enough to invest the attention to do so.
Take "they" as a wide spectrum of those who are employed in this industry.