In the grassy area at my school rec center where I do my plyo workout, there's only a bench I can do depth jumps on.  It's only like 15~18"...  There's nothing higher there.
I was thinking, when this bench gets too easy, can I do something like where I kind of jump off the bench like 6", mimicking a 21~24" depth jump?  Or is there something else going on that it changes the dynamics and it's not really a depth jump?