Sometimes the obvious countermeasures are the easiest ones to forget

found on Reddit

Stay out of the water, stay out of the bad part of town, stay out of untrustworthy websites, etc. If you always remember those sorts of obvious things, good for you, but plenty of people need reminders, and some never knew in the first place. So don't just remember for your own sake, remember to share those steps with others as well.

Death defying stealth

found on Reddit

I suppose most defensive stealth is attempting to avoid death, but usually it doesn't involve becoming temporarily dead in the process. 

Kill-a-bites of data lost

from here and here (image source)

While the article is old news, the image of a shark biting undersea cables apparently recaptured people's imagination on twitter recently so here we are

Apparently that's now how they work

from here

While the news article does explain the theory about how the technology is supposed to work, it sounds laughably like snake-oil to me. I wouldn't trust anything short of a metal cage to protect me from a shark, until such time other effective preventative measures become well known and common place.