oldnode = {}
minetest.register_globalstep(function(dtime)
	for _,player in ipairs(minetest.get_connected_players()) do
		local pos = player:getpos()
		pos.y = pos.y + 0.2
		local newnode = minetest.env:get_node(pos).name
		if oldnode ~= nil then
			if newnode == "default:water_flowing" and oldnode[player:get_player_name()] == "air" or newnode == "default:water_source" and oldnode[player:get_player_name()] == "air" then
				for i = 1,math.random(7,20) do
					minetest.env:add_entity(pos, "testing:bubble")
				end
				minetest.sound_play("splash",
				{
					to_player = player:get_player_name(),
					gain = 1.0,
				})
			end
		end
		oldnode[player:get_player_name()] = newnode
	end
end)

bubble = {
	physical = false,
	collisionbox = {0,0,0,0,0,0},
	visual = "sprite",
	textures = {"bubble.png"},
	timer = 0,
	visual_size = {x=0.2, y=0.2}
}
bubble.on_activate = function(self)
	local y = math.random()
	local z = math.random(-1,1) * math.random()
	local x = math.random(-1,1) * math.random()
	self.object:setvelocity({x=x,y=y,z=z})
end
bubble.on_step = function(self)
	self.timer = self.timer + 0.01
	if self.timer > math.random() then
		self.object:remove()
	end
end
minetest.register_entity("testing:bubble", bubble)