diff --git a/src/layers/shipwrecks/index.js b/src/layers/shipwrecks/index.js
index f2451d7bd..c4599303c 100644
--- a/src/layers/shipwrecks/index.js
+++ b/src/layers/shipwrecks/index.js
@@ -29,6 +29,8 @@ const CARD_HOST_OPTIONS = Object.freeze({
   moving: false,
 });
 const MAX_CARD_LINES = 14;
+/** Wrecks not refreshed for this long leave the map (the proxy's own limit). */
+const MAX_SHOWN_AGE_MS = 7 * 24 * 60 * 60 * 1000;
 /**
  * Marker size in pixels: grows with the death toll, from 16 px (no deaths known) to 36 px (about a thousand or more).
  */
@@ -67,6 +69,7 @@ export function createShipwrecksLayer({
   openExternal = null,
   // One collection for every wreck marker (thousands of them): far cheaper to
   // draw and rebuild than an entity each. Tests pass a fake.
+  now = () => Date.now(),
   createMarkers = (scene) =>
     new Cesium.BillboardCollection({
       scene,
@@ -378,7 +381,7 @@ export function createShipwrecksLayer({
         // The page checks every 6 h; the proxy refreshes once a day. Only a
         // new snapshot rebuilds the markers.
         const unchanged =
-          snapshot.version !== null &&
+          typeof snapshot.version === 'string' &&
           snapshot.version === _snapshot?.version &&
           _pins.length > 0;
         _snapshot = snapshot;
@@ -396,6 +399,15 @@ export function createShipwrecksLayer({
           return false;
         console.warn('[Data:Shipwrecks] Fetch error:', error);
         _lastError = error?.message || msg('Shipwrecks unavailable');
+        // What is on the map was not refreshed: say so, and drop it once it
+        // is older than the proxy itself would serve.
+        if (_snapshot) {
+          const age = now() - (_snapshot.fetchedAt ?? now());
+          if (age > MAX_SHOWN_AGE_MS) {
+            _snapshot = null;
+            rebuild([]);
+          } else _snapshot = { ..._snapshot, stale: true };
+        }
         notifyRow();
         return false;
       } finally {
diff --git a/src/layers/shipwrecks/index.test.mjs b/src/layers/shipwrecks/index.test.mjs
index d42aedaf1..92cb05733 100644
--- a/src/layers/shipwrecks/index.test.mjs
+++ b/src/layers/shipwrecks/index.test.mjs
@@ -51,7 +51,7 @@ function fakeMarkers() {
   return collection;
 }
 
-function harness({ snapshots } = {}) {
+function harness({ snapshots, now = () => 1 } = {}) {
   const markers = fakeMarkers();
   const primitives = [];
   const cards = [];
@@ -81,6 +81,7 @@ function harness({ snapshots } = {}) {
       getSnapshot({ signal }) {
         requests.push(signal);
         const next = queue.shift();
+        if (next instanceof Error) return Promise.reject(next);
         return next instanceof Promise ? next : Promise.resolve(next);
       },
     },
@@ -105,6 +106,7 @@ function harness({ snapshots } = {}) {
     picking,
     pointer: { isPointerFree: () => true },
     openExternal: (url) => opened.push(url),
+    now: () => now(),
   });
   layer.init(viewer);
   return {
@@ -244,3 +246,48 @@ test('the year pickers list only years with a wreck, and each era is counted', a
     [0, 2, 0, 0],
   );
 });
+
+test('a source without a version rebuilds on every new snapshot', async () => {
+  const bare = (records) => {
+    const value = snapshot(records);
+    delete value.version;
+    return value;
+  };
+  const h = harness({
+    snapshots: [
+      bare([wreck('a')]),
+      bare([wreck('a'), wreck('b')]),
+      { ...snapshot([wreck('a')]), version: null },
+      { ...snapshot([wreck('a'), wreck('b'), wreck('c')]), version: null },
+    ],
+  });
+  h.layer.enable();
+  for (const expected of [1, 2, 1, 3]) {
+    await h.layer.update();
+    assert.equal(h.markers.billboards.length, expected);
+  }
+});
+
+test('a failed refresh marks the shown wrecks stale, and clears them after seven days', async () => {
+  const DAY = 24 * 60 * 60 * 1000;
+  let clock = 1;
+  const h = harness({
+    now: () => clock,
+    snapshots: [
+      snapshot([wreck('a')]),
+      new Error('Shipwrecks unavailable (HTTP 502)'),
+      new Error('Shipwrecks unavailable (HTTP 502)'),
+    ],
+  });
+  h.layer.enable();
+  await h.layer.update();
+  assert.equal(h.layer.getStats().stale, false);
+  clock = 1 + 2 * DAY;
+  assert.equal(await h.layer.update(), false);
+  assert.equal(h.layer.getStats().stale, true);
+  assert.equal(h.layer.getStats().count, 1, 'still shown, as stale');
+  clock = 1 + 8 * DAY;
+  await h.layer.update();
+  assert.equal(h.layer.getStats().count, 0, 'expired wrecks leave the map');
+  assert.equal(h.markers.billboards.length, 0);
+});