"Lead," Rick said. "Part of the slug."
"Good thing it didn't rupture the tank."
Rick shuddered. "If it had, I'd have been out of air suddenly and would've had to come up. Listen, Scotty. My plan is a simple one. I'll take your tank, since you have the most air, and swim right into the cove, find the 'what's-it' and swim out again. If it's too heavy to tow far, I can at least wrestle it part of the way, and then bury it in the mud. Meanwhile, you get the boat out where it's clear and be ready to pick me up."
"They'll see your bubbles, but they can't do anything about it with rifles," Scotty pointed out. "One thing they can do, though, is jump in after you. The cove isn't so deep that a pair of good swimmers couldn't tackle you. The lung wouldn't improve your chances by much."
"Too true," Rick observed. "But what else can we try?"
Scotty thought it over. "Listen, we'll take the boat out right now. You'll have to do the diving, because you know about where the thing is, and I don't. When we get out, you go over the side. I'll run around to the river, opposite where the guards are standing, and raise a little fuss. That might draw their attention away from the cove."
"Okay." It made sense to Rick. "They'll see both of us in the boat, but they won't see me get out. Only you'd better plan our course. I have no aching desire to collect a rifle slug where it hurts."
"They may not shoot if they see we're leaving," Scotty pointed out.
"Uh-huh. And they might shoot, anyway."
"They might. But we'll be moving fast, and I'll swing that boat from side to side like a swivel-hipped fullback. Let's get going. We don't want too much daylight."