It's a guessing game, trying to catch fish with hook and line.

Anglers can use the latest in GPS and sonar technology to anchor right over what they hope is a reef or wreck loaded with fish, but when it comes right down to it, most fishermen really don't know what's down there, 60 or 80 feet below their boat.

Unless you're Jason Ward. Then you put on your scuba gear and go find out.

Ward is part of a growing contingent of recreational speargunners hunting the ocean bottom off Charleston. Though he also loves to troll for dolphin, wahoo and billfish, Ward is hooked on diving into the unknown for grouper, snapper and other bottom dwellers.

Seven years after earning his first certification, Ward now completes 40 to 50 dives off Charleston's coast every year.

"I've hunted and fished my entire life, and spearfishing is the perfect hybrid," Ward says. "One of the things I love most about it is that you've got this vision of what it looks like down there, after bottom fishing on these same spots for years. But that day you get to go see what is down there it pretty much looks nothing like that."

This ability to dive down and observe the action in 60 to 120 or so feet of water has given Ward and his fellow speargunners unprecedented knowledge about popular game fish and their habitats. Ward and his buddies sometimes even get to observe rod-and-reel angling from the fish's perspective.

"We let people fish while we are diving, and sometimes actually get to see them catch fish," Ward says. "When you witness this a few times, it's pretty easy to see why most bottom fishermen can easily catch black seabass, triggers and other smaller species. "¦ Groupers and snappers tend to be very leery and don't rush right out at a bait. On the contrary, triggerfish and black seabass act like piranhas. We've seen several times where the bait was coming down pretty quickly and you see 10 to 12 of them rocket up out of nowhere and meet the bait before it even hits the bottom."

""¦ It really goes to show you that you cannot accurately measure what is on the bottom from hook and line."

Like most speargunners based in Charleston, Ward targets snappers, groupers and other such structure-oriented fish found at wrecks and natural hard-bottom areas in 60 to 120 feet of water. Lowcountry spearfishermen concentrate mostly on bottom fish rather than pelagic species like dolphin and wahoo primarily because open-water fish are harder to find, and they can easily swim away from a diver. Because grouper-snapper species hold to structure, "you might not be able to get a shot on the one you want, but hopefully, you'll get a shot at one of them," Ward says.

Though federal regulators have enacted new closed seasons for some bottom species and tightened restrictions on others, the interest in spearfishing remains strong, and Lowcountry anglers had been anxiously awaiting May 1, when a four-month ban on shallow-water grouper catches was set to end.

According to Ward, here's how a typical spearfishing trip works:

Most speargunners dive with friends on private boats, though spearfishing charters are available through Lowcountry Scuba in Mount Pleasant. The average day usually consists of two to five dives per diver, spaced out between the required surface time intervals as outlined by dive computers and charts.

Most spearfishing boats don't anchor. Keeping the boat mobile saves a reef from anchor damage and makes it easier to pick up divers once they resurface. This is especially helpful in case of an emergency, Ward says.

"It would be a lot of effort for that boat to get off anchor to come get you."

Ward and his buddies typically deploy a temporary marking buoy to show where the dive started, and they leave at least two people onboard while divers are under water.

Most speargunning is done "free-shaft," in which the speargun does not have a line attaching it to a spear. Since they're on the bottom and hunting fish that stay close to structure, the lack of a line is usually not a problem, Ward says. Divers simply shoot the fish, then swim over and pick it up.

"Part of it is a safety thing," Ward says. "I don't want to be attached to a fish in 100 feet and have him pull me around. I've seen lines gets wrapped up in people's gear.

"You get a nice shot on him, and he's pretty much incapacitated. He might swim 10 or 15 feet, or if you're a horrible shot you might have to chase him down a bit."

Speargunners usually thread each fish they shoot on a big metal loop. Near the end of each dive, they'll attach a "lift bag" to the ring, and using air from their scuba tanks, send their catch to the surface, where the boat picks it up. The divers can then take their time and concentrate on resurfacing procedures, which involve a "safety stop" for decompression.

Sound simple? Not quite.

"Contrary to popular belief," Ward says, "you don't just swim up to a fish and shoot it. Fish are not stupid. They know what a predator looks like. If you look like a predator in the water, you're not even going to get close enough to shoot them. You have to learn techniques to stalk them, to sneak up on them.

""¦ Fish tend to choose whether you see them or not. Certain days they will be curious. Other days, they will stay well out of range or at the edge of visibility."

There's also the matter of knowing what kind of fish is lurking ahead of you in the murky depths. Unlike hook-and-line fishing, speargunning isn't exactly a catch-and-release activity.

"Light penetrates fairly well down to the depths that we dive, but you start losing color not far from the surface," Ward says. "Your reds, browns and oranges are the first to disappear. A red snapper at 100 feet looks silver." That's why it's important for divers to learn other distinguishing characteristics."

Just spotting fish under 80 or so feet of water, much less telling one species from another, takes training, practice and patience.

"Interestingly enough, a fish with a smooth silver skin like an African pompano or mackerel looks almost invisible from just a few yards away," Ward says. "It's like nature's camouflage. Often the first thing that you see is the outline of the fish or its fins or eyes before you see the actual body.

""¦ Grouper can change colors almost like chameleons. "¦ Gag groupers that are moving across the sand often look almost a light gray or a white color, which gives them good camouflage. However, if they are holding tight into the rocks or in caves, they tend to carry a very dark brown color, which helps them blend in incredibly well."

Though concentrating on structure-oriented fish gives speargunners a bit of a leg up when it comes to finding fish, there's no guarantee of success.

"Fish tend to move around a bit," Ward says. "I remember diving a spot once at the end of the day, starting out with half a tank of air just to scout it out for next time. As Murphy's Law would have it, it was absolutely covered with mature gag grouper, but we really didn't have the air capacity to stay down for more than a few minutes. We came back three days later and only saw a handful of fish!"

Years of experience have given Ward a few general rules of thumb to finding quality fish.

"Grouper seem to get bigger the deeper you go," he says. "We seldom see large scamp groupers in less than 105 feet of water, but we do see a ton of them in the 2- to 4-pound range. Once you cross that magical 105-foot threshold, you suddenly start to see them up to 12 to 15 pounds sometimes. Our best last year was in 110 feet of water at 21 pounds.

"Gags seem to follow the same pattern. On my last dive of 2009, we dove in 67 feet of water within sight of Charleston. We probably saw 100 to 200 gag grouper, but the biggest was probably around 12 pounds, with most being in that 3- to 6-pound range. However, early that day, we saw all of the 18- to 20-pound gags that you wanted in 80 to 100 feet of water."

The presence of prey also seems to be one of the best indicators of good hunting grounds.

"Like clockwork, when there is a large school of cigar minnows on a reef, there seems to be a healthy population of large grouper and snapper feeding on them. "¦ If there are no cigar minnows around, sometimes schools of tomtates seem to be enough to hold the attention of groupers.

"But one thing is for sure, grouper and snapper eventually need to eat, and occasionally we see reefs temporarily abandoned by the larger fish when the bait is not there."

Contact Matt Winter, Tideline senior editor, at 843-834-3762 or matt@tidelinemagazine.com.