the blobs are separate.
but essentially, yeah. pick a blob. pretty it up. get on over to the center blob.
/./
...
/./
. = blob
Yes, enough for you to complete that attack. In general, you have the option of defending an attack on the previous blob, or having it switch, then doing it. Personally, I'd wait to switch until after my defense.
But yeah, if you're attacking with water, it'd go with you, but solely enough for that attack. If you're charging an attack though, some can come with you, or you can just charge it until your return. I lean latter since you wouldn't actually be attacking with it.