Motorcycle Mud Flaps Can Someone Tell Me About The Splashguard On A Whale?

Can someone tell me about the splashguard on a whale? - motorcycle mud flaps

I have tried to find a definition which reads as follows:
a curved piece on the wheel of a bicycle or motorcycle to protect the passage of water or mud thrown up by wheels)

My concern is I have a scene on a whale and can not really understand what they mean:

They also have a ridge that crosses the top of the head and a big stir in the presence of their two blowholes.

Can someone explain?