A whale is an individual, a business, a cryptocurrency exchange, or even an institution with sizeable holdings of a particular cryptocurrency, who often also has a significant amount of capital invested in the cryptocurrency market as a whole.
Bear Whales use their capital “size” to drive down cryptocurrency prices in hopes of profiting from the price decline.
Whales can place and remove sell walls on a CEX’s order book continuously, manipulating other traders to sell off their assets early because they see the sell wall.
This action could drive down both demand and price, and they (the other traders) want to get out before that happens.
Whales use sell walls to bluff other traders into putting their sell orders below the sell wall, causing price to move down.