diff --git a/src/apps/gameboard/views.py b/src/apps/gameboard/views.py
index 671e303..9f16e16 100644
--- a/src/apps/gameboard/views.py
+++ b/src/apps/gameboard/views.py
@@ -170,11 +170,16 @@ def toggle_game_kit_sections(request):
 def my_sea(request):
     """Shell view for the My Sea standalone page.
 
-    Sprint 3 scaffolding only — the page will host the gatekeeper /
-    sig-select / sea-select phase reskin for solo-user draws in later
-    sprints. For now it just renders the empty skeleton.
+    Sprint 3 scaffolding + Sprint 4b sign-gate. The gate fires when the
+    user has no saved significator — a Look!-formatted Brief-style line
+    nudges them to /billboard/my-sign/ (FYI) or back to /gameboard/
+    (BACK) before the draw UX can be reached. With a sig set, the draw
+    shell renders normally (gatekeeper / sig-select / sea-select land
+    in Sprints 5-9).
     """
+    user_has_sig = request.user.significator_id is not None
     return render(request, "apps/gameboard/my_sea.html", {
+        "user_has_sig": user_has_sig,
         "page_class": "page-gameboard page-my-sea",
     })
 
diff --git a/src/functional_tests/test_game_my_sea.py b/src/functional_tests/test_game_my_sea.py
new file mode 100644
index 0000000..065846b
--- /dev/null
+++ b/src/functional_tests/test_game_my_sea.py
@@ -0,0 +1,161 @@
+"""FTs for the My Sea standalone page sign-gate.
+
+Sprint 4b of [[project-my-sea-roadmap]]. The /gameboard/my-sea/ page is
+gated behind sig selection — when `user.significator` is None, render a
+Look!-formatted Brief-style line w. FYI (→ /billboard/my-sign/) + BACK
+(→ /gameboard/) instead of the draw UX. The My Sea applet on /gameboard/
+mirrors the gate hint in its empty-state slot.
+"""
+from selenium.webdriver.common.by import By
+
+from .base import FunctionalTest
+from apps.applets.models import Applet
+from apps.epic.models import personal_sig_cards
+from apps.lyric.models import User
+
+
+def _seed_gameboard_applets():
+    """My Sea + the rest of the gameboard applets so /gameboard/ renders
+    without missing-applet errors during the applet-side assertions."""
+    for slug, name, cols, rows, ctx in [
+        ("my-sea", "My Sea", 12, 4, "gameboard"),
+        ("game-kit", "Game Kit", 4, 6, "gameboard"),
+        ("my-palette", "My Palette", 4, 4, "gameboard"),
+        ("my-games", "My Games", 4, 4, "gameboard"),
+    ]:
+        Applet.objects.get_or_create(
+            slug=slug,
+            defaults={"name": name, "context": ctx,
+                      "default_visible": True, "grid_cols": cols, "grid_rows": rows},
+        )
+
+
+class MySeaSignGateTest(FunctionalTest):
+    """Sign-gate UX on the standalone /gameboard/my-sea/ page + the
+    /gameboard/ My Sea applet. User without a saved sig sees a Look!-
+    formatted nudge w. FYI to the picker + BACK to the gameboard."""
+
+    serialized_rollback = True
+
+    def setUp(self):
+        super().setUp()
+        _seed_gameboard_applets()
+        self.email = "sea@test.io"
+        self.gamer = User.objects.create(email=self.email)
+        sig_pile = personal_sig_cards(self.gamer)
+        self.target_card = sig_pile[0] if sig_pile else None
+        self.assertIsNotNone(
+            self.target_card,
+            "personal_sig_cards(user) returned no cards — check Earthman seed",
+        )
+
+    # ── Test 1 ───────────────────────────────────────────────────────────────
+
+    def test_no_sig_renders_lookline_gate_on_standalone_page(self):
+        """User without significator → /gameboard/my-sea/ shows the Look!-
+        formatted Brief-style line w. the gate copy + FYI + BACK buttons."""
+        self.create_pre_authenticated_session(self.email)
+        self.browser.get(self.live_server_url + "/gameboard/my-sea/")
+        gate = self.wait_for(
+            lambda: self.browser.find_element(
+                By.CSS_SELECTOR, ".my-sea-sign-gate"
+            )
+        )
+        text = gate.text
+        self.assertIn("Look!", text)
+        self.assertIn("pick your sign", text.lower())
+        self.assertIn("drawing the Sea", text)
+        # FYI + BACK action buttons
+        fyi = gate.find_element(By.CSS_SELECTOR, ".my-sea-sign-gate__fyi")
+        self.assertTrue(fyi.is_displayed())
+        back = gate.find_element(By.CSS_SELECTOR, ".my-sea-sign-gate__back")
+        self.assertTrue(back.is_displayed())
+
+    # ── Test 2 ───────────────────────────────────────────────────────────────
+
+    def test_gate_fyi_links_to_my_sign_picker(self):
+        """FYI button is an `<a href>` pointing at /billboard/my-sign/."""
+        self.create_pre_authenticated_session(self.email)
+        self.browser.get(self.live_server_url + "/gameboard/my-sea/")
+        fyi = self.wait_for(
+            lambda: self.browser.find_element(
+                By.CSS_SELECTOR, ".my-sea-sign-gate__fyi"
+            )
+        )
+        href = fyi.get_attribute("href") or ""
+        self.assertTrue(
+            href.endswith("/billboard/my-sign/"),
+            f"FYI should link to /billboard/my-sign/, got {href!r}",
+        )
+
+    # ── Test 3 ───────────────────────────────────────────────────────────────
+
+    def test_gate_back_links_to_gameboard(self):
+        """BACK button is an `<a href>` pointing at /gameboard/."""
+        self.create_pre_authenticated_session(self.email)
+        self.browser.get(self.live_server_url + "/gameboard/my-sea/")
+        back = self.wait_for(
+            lambda: self.browser.find_element(
+                By.CSS_SELECTOR, ".my-sea-sign-gate__back"
+            )
+        )
+        href = back.get_attribute("href") or ""
+        self.assertTrue(
+            href.endswith("/gameboard/"),
+            f"BACK should link to /gameboard/, got {href!r}",
+        )
+
+    # ── Test 4 ───────────────────────────────────────────────────────────────
+
+    def test_with_sig_skips_gate_and_renders_draw_shell(self):
+        """User w. saved significator → no .my-sea-sign-gate on the page;
+        draw shell renders normally (Sprint 3 placeholder)."""
+        self.gamer.significator = self.target_card
+        self.gamer.save(update_fields=["significator"])
+        self.create_pre_authenticated_session(self.email)
+        self.browser.get(self.live_server_url + "/gameboard/my-sea/")
+        self.wait_for(
+            lambda: self.browser.find_element(By.CSS_SELECTOR, ".my-sea-page")
+        )
+        self.assertEqual(
+            len(self.browser.find_elements(By.CSS_SELECTOR, ".my-sea-sign-gate")),
+            0,
+            "Gate should not render when user has a saved significator",
+        )
+
+    # ── Test 5 ───────────────────────────────────────────────────────────────
+
+    def test_no_sig_applet_mirrors_gate_with_fyi_link(self):
+        """On /gameboard/, the My Sea applet's empty state shows the same
+        Look!-formatted gate w. FYI link to /billboard/my-sign/ when the
+        user has no significator. Provides a consistent UX across surfaces."""
+        self.create_pre_authenticated_session(self.email)
+        self.browser.get(self.live_server_url + "/gameboard/")
+        applet_gate = self.wait_for(
+            lambda: self.browser.find_element(
+                By.CSS_SELECTOR, "#id_applet_my_sea .my-sea-sign-gate"
+            )
+        )
+        self.assertIn("Look!", applet_gate.text)
+        fyi = applet_gate.find_element(By.CSS_SELECTOR, ".my-sea-sign-gate__fyi")
+        href = fyi.get_attribute("href") or ""
+        self.assertTrue(href.endswith("/billboard/my-sign/"))
+
+    # ── Test 6 ───────────────────────────────────────────────────────────────
+
+    def test_with_sig_applet_renders_default_empty_state(self):
+        """Applet w. saved sig → no gate, empty-state placeholder (until
+        Sprint 7 wires up the latest-draw rendering)."""
+        self.gamer.significator = self.target_card
+        self.gamer.save(update_fields=["significator"])
+        self.create_pre_authenticated_session(self.email)
+        self.browser.get(self.live_server_url + "/gameboard/")
+        self.wait_for(
+            lambda: self.browser.find_element(By.CSS_SELECTOR, "#id_applet_my_sea")
+        )
+        self.assertEqual(
+            len(self.browser.find_elements(
+                By.CSS_SELECTOR, "#id_applet_my_sea .my-sea-sign-gate"
+            )),
+            0,
+        )
diff --git a/src/static_src/scss/_gameboard.scss b/src/static_src/scss/_gameboard.scss
index d9b4e4e..e14cfe4 100644
--- a/src/static_src/scss/_gameboard.scss
+++ b/src/static_src/scss/_gameboard.scss
@@ -161,3 +161,47 @@ body.page-gameboard {
         }
     }
 }
+
+// ─── My Sea sign-gate ────────────────────────────────────────────────────────
+// Sprint 4b of [[project-my-sea-roadmap]]. Renders when User.significator
+// is None, on both the standalone /gameboard/my-sea/ page AND the
+// /gameboard/ My Sea applet. Look!-formatted Brief-style line w. FYI
+// (→ /billboard/my-sign/) + BACK (→ /gameboard/) action buttons. Inline
+// content (not portaled like .note-banner) — it IS the page content
+// until a sig is picked, not a transient nudge.
+.my-sea-sign-gate {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    gap: 1rem;
+    padding: 1.5rem;
+    color: rgba(var(--terUser), 1);
+
+    .my-sea-sign-gate__line {
+        text-align: center;
+        font-size: 1.1rem;
+        line-height: 1.4;
+        margin: 0;
+        // --terUser ink mirrors the gate's accent + signals "do this
+        // first" visually distinct from the body's standard --secUser.
+        color: rgba(var(--terUser), 1);
+    }
+
+    .my-sea-sign-gate__actions {
+        display: flex;
+        gap: 1rem;
+        align-items: center;
+    }
+
+    // Applet variant — denser layout, omits BACK (the user is already on
+    // the gameboard). Smaller line + just the FYI action surviving.
+    &.my-sea-sign-gate--applet {
+        padding: 0.5rem;
+        gap: 0.5rem;
+
+        .my-sea-sign-gate__line {
+            font-size: 0.85rem;
+        }
+    }
+}
diff --git a/src/templates/apps/gameboard/_partials/_applet-my-sea.html b/src/templates/apps/gameboard/_partials/_applet-my-sea.html
index ea119f7..7dee233 100644
--- a/src/templates/apps/gameboard/_partials/_applet-my-sea.html
+++ b/src/templates/apps/gameboard/_partials/_applet-my-sea.html
@@ -4,7 +4,17 @@
 >
     <h2><a href="{% url 'my_sea' %}">My Sea</a></h2>
     <div class="my-sea-scroll">
-        {% if latest_draw_cards %}
+        {% if not request.user.significator_id %}
+            {# Sprint 4b applet-gate mirror — same Look!-formatted nudge as #}
+            {# the standalone page so the UX is consistent across surfaces. #}
+            <div class="my-sea-sign-gate my-sea-sign-gate--applet">
+                <p class="my-sea-sign-gate__line">
+                    Look!&mdash;pick your sign before drawing the Sea.
+                </p>
+                <a class="btn btn-info my-sea-sign-gate__fyi"
+                   href="{% url 'billboard:my_sign' %}">FYI</a>
+            </div>
+        {% elif latest_draw_cards %}
             {% for card in latest_draw_cards %}
                 <div class="my-sea-card" data-position="{{ card.position }}">
                     <span class="fan-corner-rank">{{ card.corner_rank }}</span>
diff --git a/src/templates/apps/gameboard/my_sea.html b/src/templates/apps/gameboard/my_sea.html
index 736492c..9994a28 100644
--- a/src/templates/apps/gameboard/my_sea.html
+++ b/src/templates/apps/gameboard/my_sea.html
@@ -6,8 +6,27 @@
 
 {% block content %}
     <div class="my-sea-page">
-        {# Sprint 3 shell only — gatekeeper / sig-select / sea-select phases #}
-        {# will land here in later sprints of the My Sea roadmap.            #}
-        <p class="my-sea-page__empty">No draws yet—the depths remain unfathomable.</p>
+        {% if not user_has_sig %}
+            {# Sprint 4b sign-gate. The draw UX is gated behind a saved      #}
+            {# significator — render a Look!-formatted Brief-style line w.  #}
+            {# FYI (→ /billboard/my-sign/) + BACK (→ /gameboard/) until the #}
+            {# user picks a sign. Inline (not portaled like .note-banner)   #}
+            {# because the gate IS the page content, not a transient nudge. #}
+            <div class="my-sea-sign-gate">
+                <p class="my-sea-sign-gate__line">
+                    Look!&mdash;pick your sign before drawing the Sea.
+                </p>
+                <div class="my-sea-sign-gate__actions">
+                    <a class="btn btn-cancel my-sea-sign-gate__back"
+                       href="{% url 'gameboard' %}">BACK</a>
+                    <a class="btn btn-info my-sea-sign-gate__fyi"
+                       href="{% url 'billboard:my_sign' %}">FYI</a>
+                </div>
+            </div>
+        {% else %}
+            {# Sprint 3 shell — gatekeeper / sig-select / sea-select phases #}
+            {# will land here in later sprints of the My Sea roadmap.       #}
+            <p class="my-sea-page__empty">No draws yet&mdash;the depths remain unfathomable.</p>
+        {% endif %}
     </div>
 {% endblock content %}