ankle-deep
birdbrained
birdwitted
cursory
depthless
epidermal
featherbrained
flighty
fluffy
frivolous
frothy
jejune
knee-deep
light
not deep
on the surface
shallow
shallow-headed
shallow-minded
shallow-pated
shallow-rooted
shallow-witted
shoal
skin-deep
slight
superficial
surface
thin
trivial
volatile