Pole spear
A one-piece (or breakdown) shaft with a loop of rubber tubing at the butt end. You slip the loop over your thumb or hand, walk your grip up the shaft to stretch and load the band, and hold that tension yourself until you release. The spear stays in your hand's control the whole time. Short range — essentially your arm plus the shaft — but dead simple, cheap, and unbeatable for learning to stalk.
Hawaiian sling
Often confused with a pole spear, but different: a Hawaiian sling is a separate handle with a band (like an underwater slingshot or bow) that a loose shaft passes through. You draw the shaft back against the band and release, and the spear leaves the sling entirely to fly free. More range than a pole spear, but you have to retrieve a separate shaft after each shot, and it's a step more complex to aim.
Speargun
A speargun uses a mechanical trigger to hold a loaded spear until you choose to fire, with far more range and power than a pole spear. It's the natural next step, but it costs more and adds mechanism to maintain. If you're weighing the jump, see our best speargun for beginners guide — many spearos start on a pole spear and move to a gun once they can reliably close the distance.