Being more than 1000 miles away from anything salty, I've mad due with the freshy spearing for nearly 4 years now.
Here's what ya need to kill things in fresh water.
1. Short gun (stock should be less than 80 cm). The fish don't get big enough, and the vis is rarely ever good enough to warrant much bigger.
2. Get a license. Most states' normal fishing license covers spearing in lakes, but there will probably be added restrictions so pay attention or the wardens will take away your gear.
3. Log on to the Department of Natural Resources (or your state's counterpart) and search for Bathymetry maps of the lake you're targeting. Pay attention to the vegetation symbols on the map (especially in the 10-25 feet zone)....that's where the fishies be hidin'.
4. Weight yourself heavy. Lying on the bottom is one of the best ways to hunt in fresh water. Since vis is usually not very good, stalking is difficult. It's better to save your O2. Find a hot spot, and just lie on the bottom and wait for them to come to you. They will.
5. Don't let any nearby fisherman see all the fish your killin. It pisses them off (especially if they aren't catching em), and some aren't the most....er.....stable of fellas, if you get my meaning. I've had some yokels buzz to within 10 feet of my float to 'prove a point'. Hearing that loud 'ticka ticka ticka' of a boat prop over your head is not anywhere you want to be. Better to attach your stringer to your float and never bring a fish out of the water.
6. Bring a buddy
; even if they do nothing more than snorkel while you hunt. Once they see all the fun you're having, they'll have a gun by the next time you go
.
That should get started. Have fun and be safe.
Ted