You first need to figure out what you want to hunt for. In the NW it’s Ling Cod. Then you need to find out when the season is open for that critter and what the rules are in regards to spearfishing. You can usually pick up a free guide to your states hunting/fishing at a local sporting goods store. What kind of equipment you use will depend on what you are hunting for.
Go get the guide first...decide what you are after and then visit the dive store.
NAUI offers a Hunter/Collector specialty course that provides good information and experience.
Happy Hunting!