Questions about Aqua exercise and ab work @ SSL

Hi SSL,

I've seen an exercise where a guy is near the corner of the pool, each hand bracing on the deck, with a partner bouncing the guys head and neck forwad, while the guy pumps his legs. it kind of looked like it could be done on the super cat and an exercise ball, but i think it was done in the pool for isokinetic reasons. what is this exercise, and what's with the head bouncing?

also, i asked a question in the basic forum, but i figured it might be answered if i put it in the elite forum: does SSL use medicine balls in their training, like how boxers do? i've got a sledge that i use for ab work, but i'm thinking about going lighter to do it faster...does that fit with SSL's methodology?

Thanks

Kyle