Yeah, without a doubt, the regulations around spearfishing can be quite confusing. In many cases, spearfishing is an afterthought when the regulations were drafted.
Some fish are completely off-limits to spearing, though open to hook and line. Some areas as well. IIRC, Collier County doesn't allow spearfishing at all in FL state waters around Collier. The Keys can get confusing as well. Several No-Take zones, and several No-Spearfishing zones.
One of the more ridiculous recent regulations is the Gulf of Mexico Descend Act, which took effect in January. This requires fishermen fishing for reef fish from recreational, charter, and commercial boats in Gulf Federal waters to have a descending device or venting tool onboard and ready to deploy. Despite many comments asking for exemption, the final rule did not add an exemption for spearfishing. So, technically, even if I don't have a rod and reel on the boat, I should still carry a descending device if spearfishing for reef fish.