Swim Under the Waves With a Breathing Device
Puzzle 7 of Safety First Hard Pack
Question is: Swim Under the Waves With a Breathing Device
and the answer is: SCUBADIVE
Word Meaning:
SCUBA — (underwater diving) An apparatus carried by a diver, which includes a tank holding compressed, filtered air and a regulator which delivers the air to the diver at ambient pressure which can be used underwater.
Definitions from Wiktionary.