The initial idioms of the letter B

be up to ears in	be up to much
be up to neck in	be up to no good
be below par	be up to scratch
be up to the mark	be up with the chickens
be up with the crows	be up with the lark
be upon	be waiting in the wings
be floating on air	be walking on eggshells
wash up	be water off a duck's back
be water under the bridge	be wearing [teacher's etc.] hat
be well away	be well in
be well up on	be well versed in (something)
be wet behind the ears	be whistling Dixie
be whistling in the dark	be wide of the mark
be wide open	be wide open to (something)
be wise to	be wise to (someone or something)