Across:
1: H2O
3: Skillfully
4: The square root of four
5: Huge
9: A large kingdom
10: The opposite of subtract
11: A walk through the wilderness
12: Very good
15: A furry swimming mammal
18: The part of the body used
for the auditory sense
19: Beings from outer space
21: A large deer like animal
22: He ___ to the park
23: The opposite of from