WordNet sense 1 ((of sleep) easily disturbed):

light

WordNet sense 2 (not deep or strong; not affecting one deeply):

shallow

WordNet sense 3 (marked by full consciousness or alertness):

waking

WordNet sense 4 (not in a state of sleep; completely conscious):

awake

WordNet sense 5 (carefully observant or attentive; on the lookout for possible danger):

open-eyed, vigilant, watchful, argus-eyed

WordNet sense 6 (very attentive or observant):

alert