diff --git a/src/rendering/water-material.js b/src/rendering/water-material.js
index f7d7f037..b57284e3 100644
--- a/src/rendering/water-material.js
+++ b/src/rendering/water-material.js
@@ -422,6 +422,86 @@ function createSegmentPatchFromCluster(cluster) {
     };
 }
 
+function createSignedDistanceToPatchRegion(point, center, axis, halfExtents) {
+    const patchPerpendicular = new Vector2(-axis.y, axis.x);
+    const patchLocalUv = new Vector2(point.clone().sub(center).dot(axis), point.clone().sub(center).dot(patchPerpendicular));
+    const regionDelta = new Vector2(Math.abs(patchLocalUv.x) - halfExtents.x, Math.abs(patchLocalUv.y) - halfExtents.y);
+    const outsideDistance = new Vector2(Math.max(regionDelta.x, 0), Math.max(regionDelta.y, 0)).length();
+    const insideDistance = Math.min(Math.max(regionDelta.x, regionDelta.y), 0);
+    return outsideDistance + insideDistance;
+}
+
+function createBoxPatchFromSegmentLoop(segments, minimumThickness) {
+    if (segments.length < 3) {
+        return null;
+    }
+    const canonicalAxes = [];
+    for (const segment of segments) {
+        if (segment.shape !== "segment") {
+            return null;
+        }
+        const axis = new Vector2(segment.axisX, segment.axisZ);
+        if (axis.lengthSq() <= WATER_CONTACT_EPSILON) {
+            continue;
+        }
+        axis.normalize();
+        if (axis.x < 0 || (Math.abs(axis.x) <= WATER_CONTACT_EPSILON && axis.y < 0)) {
+            axis.multiplyScalar(-1);
+        }
+        const existingAxis = canonicalAxes.find((candidate) => Math.abs(candidate.dot(axis)) >= 0.94);
+        if (existingAxis === undefined) {
+            canonicalAxes.push(axis);
+        }
+    }
+    if (canonicalAxes.length < 2) {
+        return null;
+    }
+    let foundOrthogonalAxes = false;
+    for (let leftIndex = 0; leftIndex < canonicalAxes.length; leftIndex += 1) {
+        for (let rightIndex = leftIndex + 1; rightIndex < canonicalAxes.length; rightIndex += 1) {
+            const leftAxis = canonicalAxes[leftIndex];
+            const rightAxis = canonicalAxes[rightIndex];
+            if (leftAxis === undefined || rightAxis === undefined) {
+                continue;
+            }
+            if (Math.abs(leftAxis.dot(rightAxis)) <= 0.35) {
+                foundOrthogonalAxes = true;
+                break;
+            }
+        }
+        if (foundOrthogonalAxes) {
+            break;
+        }
+    }
+    if (!foundOrthogonalAxes) {
+        return null;
+    }
+    const projectedPoints = [];
+    for (const segment of segments) {
+        const [startPoint, endPoint] = createSegmentEndpoints(segment);
+        projectedPoints.push(startPoint, endPoint);
+    }
+    const candidatePatch = createPatchFromProjectedPoints(projectedPoints, null, minimumThickness);
+    if (candidatePatch === null) {
+        return null;
+    }
+    const candidateAxis = new Vector2(candidatePatch.axisX, candidatePatch.axisZ);
+    if (candidateAxis.lengthSq() <= WATER_CONTACT_EPSILON) {
+        return null;
+    }
+    candidateAxis.normalize();
+    const candidateCenter = new Vector2(candidatePatch.x, candidatePatch.z);
+    const candidateHalfExtents = new Vector2(candidatePatch.halfWidth, candidatePatch.halfDepth);
+    const acceptanceDistance = Math.max(minimumThickness * 2.2, 0.14);
+    for (const point of projectedPoints) {
+        const signedDistance = createSignedDistanceToPatchRegion(point, candidateCenter, candidateAxis, candidateHalfExtents);
+        if (Math.abs(signedDistance) > acceptanceDistance) {
+            return null;
+        }
+    }
+    return candidatePatch;
+}
+
 function getTriangleMeshMergeSettings(mergeProfile, minimumThickness) {
     if (mergeProfile === "aggressive") {
         return {
@@ -541,7 +621,13 @@ function appendTriangleMeshContactPatches(patches, source, volume, inverseRotati
             });
         }
     }
-    patches.push(...mergeTriangleMeshContactPatches(rawPatches, bandMinimumThickness, source.mergeProfile));
+    const mergedPatches = mergeTriangleMeshContactPatches(rawPatches, bandMinimumThickness, source.mergeProfile);
+    const loopPatch = createBoxPatchFromSegmentLoop(mergedPatches, bandMinimumThickness);
+    if (loopPatch !== null) {
+        patches.push(loopPatch);
+        return;
+    }
+    patches.push(...mergedPatches);
 }
 
 export function collectWaterContactPatches(volume, contactBounds, patchLimit = MAX_WATER_CONTACT_PATCHES) {