How would I make this rocket launcher script NOT destroy terrain?

The current game I am making has terrain water. I was wanting to know if it was possible if you could have a rocket launcher that does no terrain damage, AND if it's possible to make the rocket launcher only do health damage, and not make everything fall apart. Oh, and if it's possible to only make the "swoosh" sound come on only once. I have a rocket launcher shot, but it repeats itself, and it gets very annoying.

Here's the code:

local Tool = script.Parent
local Launcher = Tool.Handle

local Rocket = Instance.new("Part")
Rocket.Locked = true
Rocket.BackSurface = 3
Rocket.BottomSurface = 3
Rocket.FrontSurface = 3
Rocket.LeftSurface = 3
Rocket.RightSurface = 3
Rocket.TopSurface = 3
Rocket.Size = Vector3.new(1, 2.5, 1)
Rocket.BrickColor = BrickColor.new(23)
Rocket.FormFactor = 3


local rocketMesh = Instance.new("SpecialMesh")
rocketMesh.MeshId = "http://www.roblox.com/asset/?id=31601976"
rocketMesh.TextureId = "http://www.roblox.com/asset/?id=31601599"
rocketMesh.Parent = Rocket

local debris = game:GetService("Debris")

local swooshSound
local explosionSound

local vCharacter
local vPlayer

function blow(hit, missile)
	if missile  == nil then return end
	if swooshSound then swooshSound:stop() end
	explosion = Instance.new("Explosion")
	explosion.Position = missile.Position
	-- find instigator tag
	local creator = missile:FindFirstChild("creator")
	explosion.Hit:connect(function(part, distance) onPlayerBlownUp(part, distance, creator) end)
	explosion.Parent = game.Workspace	
	if explosionSound then explosionSound:Play() end
	wait(.1)
	if missile then missile:Remove() end
end

function onPlayerBlownUp(part, distance, creator)
	if part.Name == "Head" or part.Name == "Torso" then	
		local humanoid = part.Parent.Humanoid
		tagHumanoid(humanoid, creator)
	end
end

function tagHumanoid(humanoid, creator)
	-- tag does not need to expire if all explosions lethal	
	if creator ~= nil then
		local new_tag = creator:clone()
		new_tag.Parent = humanoid		
	end
end

function fire(vTarget)
	local vCharacter = Tool.Parent	
	local vHandle = Tool:findFirstChild("Handle")
	if vHandle == nil then
		print("Handle not found")
		return 
	end
	local direction = vTarget - vHandle.Position
	direction = computeDirection(direction)
	local missile = Rocket:clone()
	local pos = vHandle.Position + (direction * 10.0)		
	missile.CFrame = CFrame.new(pos,  pos + direction) * CFrame.Angles(math.pi/2, 0, 0)

	local creator_tag = Instance.new("ObjectValue")

	local vPlayer = game.Players:GetPlayerFromCharacter(vCharacter)

	if vPlayer == nil then
		print("Player not found")
	else
		if (vPlayer.Neutral == false) then -- nice touch
			missile.BrickColor = vPlayer.TeamColor
		end
	end

	local floatForce = Instance.new("BodyForce")
	floatForce.force = Vector3.new(0, missile:GetMass() * 196.1, 0.0)
	floatForce.Parent = missile

	missile.Velocity = direction * 200.0

	creator_tag.Value = vPlayer
	creator_tag.Name = "creator"
	creator_tag.Parent = missile	

	missile.Parent = game.Workspace

	if swooshSound then swooshSound:Play() end

	missile.Touched:connect(function(hit) blow(hit, missile) end)

	debris:AddItem(missile, 100.0)
end

function computeDirection(vec)
	local lenSquared = vec.magnitude * vec.magnitude
	local invSqrt = 1 / math.sqrt(lenSquared)
	return Vector3.new(vec.x * invSqrt, vec.y * invSqrt, vec.z * invSqrt)
end

Tool.Enabled = true
function onActivated()
	if not Tool.Enabled then
		return
	end

	Tool.Enabled = false

	local character = Tool.Parent;
	local humanoid = character.Humanoid
	if humanoid == nil then
		print("Humanoid not found")
		return 
	end

	swooshSound = Launcher:FindFirstChild("Swoosh")
	explosionSound = Launcher:FindFirstChild("Explosion")

	local targetPos = humanoid.TargetPoint

	fire(targetPos)

	wait(0.5)

	Tool.Enabled = true
end


script.Parent.Activated:connect(onActivated)