I've seen a bit of talk on the discussions forum about how people playing as clients in online co-op are frustrated about how they die when trying to pick up rocks and you may not know it but there is a way to ensure you don't die when you try to grab a rock. I'll be telling you how to never die again when picking up a rock but its a bit more complicated than just pressing the grab button like the host does.

To cut to the chase, the way you pick up a rock as the client is to:

1. Crouch in front of the rock (ensure you are close enough to grab it)
   
   
   
   
2. While still crouching, grab the rock, doing so will make you eat the rock
   
   
   
   
3. Jump while still crouching and holding the rock with your grab button
   
   
   
   
4. If you did it right you will be alive and holding the rock, you can now release the crouch button
   
   

I learned about this technique from this GDQ run (at 56:10 is a brief explanation about it) check out the full run if you're ever bored, it's funny.
https://youtu.be/dDx1FTQBcMM?&t=3370