diff --git a/challenges/2021/25-seaCucumber/README.md b/challenges/2021/25-seaCucumber/README.md
new file mode 100644
index 0000000..c610098
--- /dev/null
+++ b/challenges/2021/25-seaCucumber/README.md
@@ -0,0 +1,2 @@
+# [Day 25: Sea Cucumber](https://adventofcode.com/2021/day/25)
+
diff --git a/challenges/2021/25-seaCucumber/benchmark.json b/challenges/2021/25-seaCucumber/benchmark.json
new file mode 100644
index 0000000..81a1ac4
--- /dev/null
+++ b/challenges/2021/25-seaCucumber/benchmark.json
@@ -0,0 +1,15 @@
+{
+  "day": 25,
+  "dir": "challenges/2021/25-seaCucumber",
+  "implementations": {
+    "Python": {
+      "part.1.avg": 1.2896365237236023,
+      "part.1.max": 1.4006781578063965,
+      "part.1.min": 1.2583773136138916,
+      "part.2.avg": 0.000003247261047363281,
+      "part.2.max": 0.000013828277587890625,
+      "part.2.min": 0.0000016689300537109375
+    }
+  },
+  "numRuns": 100
+}
\ No newline at end of file
diff --git a/challenges/2021/25-seaCucumber/info.json b/challenges/2021/25-seaCucumber/info.json
new file mode 100644
index 0000000..84e32fb
--- /dev/null
+++ b/challenges/2021/25-seaCucumber/info.json
@@ -0,0 +1,15 @@
+{
+    "inputFile": "input.txt",
+    "testCases": {
+        "one": [
+            {
+                "input": "v...>>.vv>\n.vv>>.vv..\n>>.>v>...v\n>>v>>.>.v.\nv>v.vv.v..\n>.>>..v...\n.vv..>.>v.\nv.v..>>v.v\n....v..v.>",
+                "expected": "58"
+            }
+        ],
+        "two": []
+    },
+    "incorrect": {
+        "one": ["406", "312"]
+    }
+}
\ No newline at end of file
diff --git a/challenges/2021/25-seaCucumber/py/__init__.py b/challenges/2021/25-seaCucumber/py/__init__.py
new file mode 100644
index 0000000..f4114bf
--- /dev/null
+++ b/challenges/2021/25-seaCucumber/py/__init__.py
@@ -0,0 +1,94 @@
+from typing import Any, List, Tuple, Dict
+from aocpy import BaseChallenge
+
+
+CUCUMBER_EAST = ">"
+CUCUMBER_SOUTH = "v"
+EMPTY = "."
+
+
+Point = Tuple[int, int]
+SeaBed = Dict[Point, str]
+
+
+def parse(instr: str) -> SeaBed:
+    lines = instr.strip().splitlines()
+    o: SeaBed = {}
+    for y, line in enumerate(lines):
+        for x, char in enumerate(line):
+            o[(x, y)] = char
+    return o
+
+
+def iterate_once(sea_bed: SeaBed) -> bool:
+    # returns true if moves were made
+
+    moves_made = False
+
+    changes: SeaBed = {}
+
+    def get_point_state(p: Point) -> str:
+        # if p in changes:
+            # return changes[p]
+        return 
+
+    # eastbound
+    for point in sea_bed:
+        point_content = sea_bed[point]
+
+        if point_content != CUCUMBER_EAST:
+            continue
+
+        x, y = point
+
+        next_point = (x + 1, y)
+        if next_point not in sea_bed:
+            next_point = (0, y)
+
+        if sea_bed[next_point] == EMPTY:
+            moves_made = True
+            changes[next_point] = point_content
+            changes[point] = EMPTY
+
+    for point in changes:
+        sea_bed[point] = changes[point]
+
+    changes = {}
+
+    # southbound
+    for point in sea_bed:
+        point_content = sea_bed[point]
+
+        if point_content != CUCUMBER_SOUTH:
+            continue
+
+        x, y = point
+
+        next_point = (x, y + 1)
+        if next_point not in sea_bed:
+            next_point = (x, 0)
+
+        if sea_bed[next_point] == EMPTY:
+            moves_made = True
+            changes[next_point] = point_content
+            changes[point] = EMPTY
+
+    for point in changes:
+        sea_bed[point] = changes[point]
+
+    return moves_made
+
+
+class Challenge(BaseChallenge):
+
+    @staticmethod
+    def one(instr: str) -> int:
+        sea_bed = parse(instr)
+        i = 1
+        while iterate_once(sea_bed):
+            i += 1
+        return i
+
+    @staticmethod
+    def two(instr: str) -> int:
+        return -1
diff --git a/challenges/2021/README.md b/challenges/2021/README.md
index 09702dc..b94433d 100644
--- a/challenges/2021/README.md
+++ b/challenges/2021/README.md
@@ -34,6 +34,10 @@ Solutions to the [2021 Advent of Code](https://adventofcode.com/2021).
 | 20 - Trench Map \*                  | ★ ★                | [Python](20-trenchMap/py), [Nim](20-trenchMap/nim)                                                      | Took a moment to realise that the infinite grid alternates between lit and unlit, and even then I had to look at someone else's solution to realise it. |
 | 21 - Dirac Dice                     | ★ ☆                | [Python](21-diracDice/py)                                                                               | Couldn't be bothered with part two - I've got too much going on at the moment to spend a lot of time thinking about it.                                 |
 | 22 - Reactor Reboot                 | ★ ★                | [Python, OpenSCAD and Blender](22-reactorReboot/)                                                       | I did not expect to end up using 3D CAD software to complete AoC...                                                                                     |
+| 23 - Amphipod                       | Unattempted        |                                                                                                         |                                                                                                                                                         |
+| 24 - Arithmetic Logic Unit          | Unattempted        |                                                                                                         |                                                                                                                                                         |
+| 25 - Sea Cucumber                   | ★ ☆                | [Python](25-seaCucumber/py)                                                                             | Missing some stars :(                                                                                                                                   |
+
 
 <!-- PARSE END -->
 
diff --git a/challenges/2021/running-times.png b/challenges/2021/running-times.png
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