Many times whales and other mammals get an infection which disturbs their equillibrium and their sense of direction is affected, causing them to lose the ability to become disoriented. It would be like a human having vertigo and not being able to stand and walk straight. They get close to shallow water and don't know which way to go to get back to the deep.Being they tend to swim in numbers, other blindly follow and end up in dire straits...weedbychoice