deep

See:

be in deep shit be in deep water be in too deep be knee-deep in Beauty is only skin deep Beauty is only skin-deep between a rock and a hard place between the devil and the deep blue sea cork high and bottle deep

deep down deep pockets deep-six dig deep dig down go deep go off the deep end in deep in deep shit

in deep water jump off the deep end knee-deep in one's deepest sympathy run deep still waters run deep take a deep breath throw in at the deep end