diff --git a/mods/MAPGEN/mcl_ocean_monument/init.lua b/mods/MAPGEN/mcl_ocean_monument/init.lua
index 8b34f2c6c0..97ca1fa6e1 100644
--- a/mods/MAPGEN/mcl_ocean_monument/init.lua
+++ b/mods/MAPGEN/mcl_ocean_monument/init.lua
@@ -1,41 +1,97 @@
 
--- Check it: `/tp 14958,8,11370` @ world seed `1`
+-- Check it:
+--	seed 1, v7 mapgen
+--	/teleport 14958,8,11370
 
 local mcl_mapgen_get_far_node = mcl_mapgen.get_far_node
 local minetest_log = minetest.log
 local minetest_place_schematic = minetest.place_schematic
 local minetest_pos_to_string = minetest.pos_to_string
+local minetest_swap_node = minetest.swap_node
 
 local path = minetest.get_modpath("mcl_ocean_monument") .. "/schematics/ocean_monument.mts"
-local water, air, ice = "mcl_core:water_source", "air", "mcl_core:ice"
+
+local water = "mcl_core:water_source"
+local air = "air"
+local ice = "mcl_core:ice"
+
+local leg_materials = {
+	"mcl_ocean:prismarine_brick",
+	"mcl_ocean:prismarine",
+}
+local what_we_can_replace_by_legs = {
+	water,
+	air,
+	"mcl_core:water_flow",
+	"mcl_core:stone",
+}
+
+local leg_search_quick_index = {}
+for _, v in pairs(leg_materials) do
+	leg_search_quick_index[v] = true
+end
+
+local leg_replace_quick_index = {}
+for _, v in pairs(what_we_can_replace_by_legs) do
+	leg_replace_quick_index[v] = true
+end
+
+local y_wanted = mcl_mapgen.OFFSET_NODES -- supposed to be -32
+local y_bottom = mcl_mapgen.overworld.min -- -62
 
 mcl_mapgen.register_chunk_generator(function(minp, maxp, seed)
 	local minp = minp
 	local y = minp.y
-	if y ~= -32 then return end
+	if y ~= y_wanted then return end
 
 	local x, z = minp.x, minp.z
 	local pr = PseudoRandom(seed)
-	for i = 1, pr:next(10,100) do
-		local pos = {x=pr:next(15,64)+x, y=pr:next(0,25)-25, z=pr:next(15,64)+z}
+
+	-- scan the ocean - it should be the ocean:
+	for i = 1, pr:next(10, 100) do
+		local pos = {x = pr:next(15, 64) + x, y = pr:next(0, 25) - 25, z = pr:next(15, 64) + z}
 		local node_name = mcl_mapgen_get_far_node(pos).name
 		if node_name ~= water then return end
 	end
-	for i = 1, pr:next(10,100) do
-		local pos = {x=pr:next(0,79)+x, y=2, z=pr:next(0,79)+z}
+
+	-- scan nodes above water level - there should be the air:
+	for i = 1, pr:next(10, 100) do
+		local pos = {x = pr:next(0, 79) + x, y = 2, z = pr:next(0,79) + z}
 		local node_name = mcl_mapgen_get_far_node(pos).name
 		if node_name ~= air then return end
 	end
+
+	-- scan ocean surface - allow only water and ice:
 	for i = 1, pr:next(10,100) do
-		local pos = {x=pr:next(0,79)+x, y=1, z=pr:next(0,79)+z}
+		local pos = {x=pr:next(0, 79)+x, y=1, z=pr:next(0,79)+z}
 		local node_name = mcl_mapgen_get_far_node(pos).name
 		if node_name ~= water and node_name ~= ice then return end
 	end
 
-	minetest_place_schematic(minp, path, tostring(pr:next(0,3)*90), nil, true)
+	-- random rotation:
+	local rotation = pr:next(0, 3)
+	local rotation_str = tostring(rotation * 90)
+	minetest_place_schematic(minp, path, rotation_str, nil, true)
 
-	minetest_log("action", "[mcl_ocean_monument] Placed at " .. minetest_pos_to_string(minp))
+	-- search prismarine legs at base level and continue them up to the bottom:
+	for x = x, maxp.x do
+		for z = z, maxp.z do
+			local pos = {x = x, y = y, z = z}
+			local node_name = mcl_mapgen_get_far_node(pos).name
+			if leg_search_quick_index[node_name] then
+				local node_leg = {name = node_name}
+				for y = y - 1, y_bottom, -1 do
+					pos.y = y
+					local next_name = mcl_mapgen_get_far_node(pos).name
+					if not leg_replace_quick_index[next_name] then
+						break
+					end
+					minetest_swap_node(pos, node_leg)
+				end
+			end
+		end
+	end
 
-	---- TODO: SET UP SOME NODES?
+	minetest_log("action", "[mcl_ocean_monument] Placed at " .. minetest_pos_to_string(minp) .. ", " .. rotation_str .. " deg.")
 
 end, mcl_mapgen.priorities.OCEAN_MONUMENT)