... Or if they did something really stupid I could do something really stupid back. Mind you my group were grown adults.
My, that's a ritual sacrifice GM type of response. Just kill the PC. Blarg.
This is the scenario, as I would have GMed it.
Player: "I will jump off the boat and swim across the rest of the river to fight the Orc's on the other side bye myself since everyone is to scared"
Me: "Make a WIS check. " (Mentally - DC 15+ I tell him, DC 10+ I give a hint)
Player: "I roll 11."
Me: Minus 1 makes ten. Thaarg isn't the smartest or wisest of warriors, is he? OK, Tharg swings his foot over the boat, almost tipping it, and looks down into the black swirling waters of indeterminate depth. The orcs don't seem to have seen him yet. He still has his heavy backpack on."
Player: "Almost tipped over the boat, huh?"
Me: "Yes" *sighs mentally* "That is certainly one danger he managed to avoid."
Player: "OK I charge the orcs. I roll a 14. Hit!"
Me: "As Tharg jumps into the dark swirling waters that are considerably deeper than they appear, he suddenly realizes there was a flaw in his cunning plan."
Player: "There's something in the water?"
Me: "Yes. Tharg. In about 60 pounds of platemail. Plus his 80 pound pack that he apparently did not take off." (*) Please make a swim skill check. Weighed down as you are, the DC is 25, but I'll allow a natural 20.
(*) Please note: real life platemail is nowhere near as heavy as D&D writers thought - tempered steel plate could be as light as 45 pounds.
Player: "I umm... but I..."
Me: Staring, unamused. "Roll."
Player: The die clatters. "A 16! Not bad! You're not going to kill me, are you?"
Me: "Cold water rushes up around him everywhere, into his gorget. He suddenly realizes has the striking inability to breathe. What is he doing?"
Player: "I... uh.. I'm stripping off! Yeah!"
Me: "What are you stripping off first? Helmet? Backpack? Pauldrons? Greaves?"
Player: (panicked) "Backpack"
Me: "Ah. Okay. Tharg's backpack is a quick-drop variety so as to allow you to quickly shed weight when about to move into combat. Tharg doesn't even need a roll for that"
Player: "So, do I get a swim reroll?"
Me: "Just a moment." To the rest of the players. "In response to your overwhelming cowardice, your bloodthirsty companion swung over the side of the boat, let out his standard war-cry, and plunged over the side. Ten seconds later, all you see are a few bubbles rising up from the depths. The water itself is too murky to see to the bottom. What are you doing?"
Player 2: "I grab my rope! And throw one end in!"
Me: "Your climbing rope? It is a thieves rope, made from silks. It is strong, thin, and light. Unfortunately, this also means it floats. Which is does, when you throw it in. You do not see anyone reach a hand out of the water to grab it."
Player 3: "I throw the anchor over the side - right near where he went in!"
Me: Smiles. "Ah. Good thinking, magician."
(A few rolls later and the warrior is safely back in the boat, somehow not having capsized it. It is only later that the magician realizes that he gave Tharg all his scrolls to carry, which are now laying waterlogged at the bottom of the river. And the PCs are treated to the sight of the Orcs, who have finally caught sight of them, rolling around on in the ground, howling in laughter. )