Before I got into cichilds, I had a pair of piranhana. I ended up getting rid of them, for exactly the reasons you mentioned. They're very timid most of the time.
I decided I'd trade them in for something else. So I put them in a gallon zip loc baggy, and headed to the fish store. On my way, of course, they went into a frenzy and started biting holes in the baggy.
So here it is, I'm driving, my girlfriend was holding the bag, there's like 4 dime sized holes in the bag, water pouring out and I'm still miles from the store.
I pulled the car over, thinking what can I do? I see a small creek next to the zoo that leads to a pond. I take the bag, walk down to the water, ask my girlfriend to look for a pop cup or something- anything so we can keep them alive.
I put the bag in the creek, hoping to quickly fill it with water. Both fish swam out of the bag... and down the creek.
This was about 15 years ago.
Ummm... oops?