It's a Geoduck: https://tinyurl.com/y2j4akpp

In chinese it's called 象拔蚌, normally it's a delicacy in south china (HK, Taiwan, Guangdong ... etc). The girl in the video most probably from north china, that's why she never see this before.

Normally people don't eat alive and biting the whole clam like that. They cut n cook it like any other clam.