There is another reason to not go more than knee deep in the North Atlantic past Columbus Day:
The water is too damn cold.
Cold water in the summer is why New Englanders don't spend a lot of time in the water. In October air temperature is also a factor.
Only about 15% - 20% of the people on the beach are in the water in the summertime .And they are not in the water for long periods of time.
Surfers in wetsuits waiting for, and riding waves are a different story-as are kayakers, and paddleboarders. A longer time for a hesitant white shark to look them over. -Tom