What do you call a flexible diving platform? I just realized this, but in international competition the diving platform isn't always elastic and flexible, but I doubt they are called a diving platform since they protrude out of the platform. You can see four of them in the lower platforms. What are they called?
They are called springboards (although they are often just called diving boards):
springboard noun [ C ]
a board that can bend, helping people to jump higher when jumping or diving into a swimming pool or when doing gymnastics
In American English, these "flexible diving platforms" are "diving boards".
A Bing image search shows that diving boards look like what the original poster had in mind.
If it is very clear from context that the object is used to dive into an artificial pool of water, the term can be shortened to "board".
The International Olympic Committee's website refers to these objects as "springboards".
Springboard is the term. When I used to swim and dive regularly, (in UK), the 'boards' were the solid platforms that had steps up to them - often at three different levels. Hence the 'top board'.
The springboard was a flexible board, often longer than the others, (its inboard end was further from the water), and sometimes adjustable in the free length over the water, to enable a variable amount of 'spring'.