uploaded the mod to github

added init.lua and depends.txt

depends.txt

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+default 

init.lua

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+--[[
+  -  Sponge mod for Minetest
+  -  water removal for survival
+
+made by Benjie/Fiftysix - 27/8/18
+
+soggy sponges can be found quite rare, deep in the sea where it is dark
+these can be cooked into dry sponges, and then placed near a liquid to remove an area of it
+they will hold the water away until they are removed.
+to use them again, they have to be cooked.
+
+sponges create a 9x9 area of air-like nodes that water can't flow through (checks for protection)
+if sponges have cleared more than 3 nodes of liquid, they become soggy sponges
+removing a sponge or soggy sponge will turn a 9x9 area of air-like nodes back into air
+(air-like nodes can be removed in protection by removing a sponge outside the protection, they are not meant to be permanent)
+]]--
+
+local area = 4
+
+
+local destruct = function(pos)  -- removing the air-like nodes
+    for x = pos.x-area, pos.x+area do
+        for y = pos.y-area, pos.y+area do
+            for z = pos.z-area, pos.z+area do
+                local n = minetest.get_node({x=x, y=y, z=z}).name
+                if n == "sponge:liquid_stop" then
+                    minetest.remove_node({x=x, y=y, z=z})
+                end
+            end
+        end
+    end
+end
+
+
+minetest.register_node("sponge:liquid_stop", {  -- air-like node
+    description = "liquid blocker for sponges",
+    drawtype = "airlike",
+    drop = {max_items=0, items={}},
+    groups = {not_in_creative_inventory=1},
+    pointable = false,
+    walkable = false,
+    sunlight_propagates = true,
+    paramtype = "light",
+    buildable_to = true,
+})
+
+
+minetest.register_node("sponge:sponge", {  -- dry sponge
+    description = "Sponge",
+    tiles = {"sponge_sponge.png"},
+    groups = {crumbly=3},
+    sounds = default.node_sound_dirt_defaults(),
+    
+    on_place = function(itemstack, placer, pointed_thing)
+        local pos = minetest.get_pointed_thing_position(pointed_thing, pointed_thing.above)
+        local name = placer:get_player_name()
+        
+        if not minetest.is_protected(pos, name) then
+            local count = 0
+            for x = pos.x-area, pos.x+area do
+                for y = pos.y-area, pos.y+area do
+                    for z = pos.z-area, pos.z+area do
+                        local n = minetest.get_node({x=x, y=y, z=z}).name
+                        local d = minetest.registered_nodes[n]
+                        if d ~= nil and (n == "air" or d["drawtype"] == "liquid" or d["drawtype"] == "flowingliquid") then
+                            local p = {x=x, y=y, z=z}
+                            if not minetest.is_protected(p, name) then
+                                if n ~= "air" then
+                                    count = count + 1  -- counting liquids
+                                end
+                                minetest.set_node(p, {name="sponge:liquid_stop"})
+                            end
+                        end
+                    end
+                end
+            end
+        
+        
+            if count > 3 then  -- only turns soggy if it removed more than 3 nodes
+                minetest.set_node(pos, {name="sponge:soggy_sponge"})
+            else
+                minetest.set_node(pos, {name="sponge:sponge"})
+            end
+            itemstack:take_item(1)
+        end
+        return itemstack
+    end,
+    
+    on_destruct = destruct
+})
+
+
+minetest.register_node("sponge:soggy_sponge", {  -- soggy sponge
+    description = "Soggy sponge",
+    tiles = {"sponge_soggy_sponge.png"},
+    groups = {crumbly=3},
+    sounds = default.node_sound_dirt_defaults(),
+    
+    on_destruct = destruct
+})
+
+minetest.register_craft({  -- cooking soggy sponge back into dry sponge
+    type = "cooking",
+    recipe = "sponge:soggy_sponge",
+    output = "sponge:sponge",
+    cooktime = 2,
+})
+
+minetest.register_decoration({  -- sponges are found deep in the sea
+    name = "sponge:sponges",
+    deco_type = "simple",
+    place_on = {"default:sand"},
+    spawn_by = "default:water_source",
+    num_spawn_by = 3,
+    fill_ratio = 0.0003,
+    y_max = -12,
+    flags = "force_placement",
+    decoration = "sponge:soggy_sponge",
+})