Can someone simplify making a jellyfish implosion?

[FoggyMountain]

Can anyone simplify making a jellyfish? I know how to do a mushroom implosion and it looks pretty similar. My friend did one but the cap was hallow in the middle and i am not sure if he went about it the right way. Can anyone help?

[earlbacher]

search jellyfish... there are many threads about it, alot of them recent...