How do scientists know the ocean floor isn't flat?

Echo sounding is the key method scientists use to map the seafloor today. The technique, first used by German scientists in the early 20th century, uses sound waves bounced off the ocean bottom.

I mean theres sand but its not actually flat. So really it depends

5.4%

explanation:

the acceptance rate for harvard is 5.4%. this means only 5 percent of people who apply actually get accepted!