Polymarket odds fall after Iran fires on tankers in Hormuz

Polymarket’s market for Strait of Hormuz traffic returning to normal by April 30 fell to 28% on April 18 after Iran reimposed shipping restrictions and Revolutionary Guard gunboats reportedly fired on at least one tanker and turned back more than 20 vessels attempting transit. The reversal followed an April 17 announcement that the waterway was “completely open” to commercial vessels under a Pakistan-brokered ceasefire.

The April 17 reopening pushed the April-May contracts higher: the May normalization market briefly reached intraday highs near 82% and the April 30 contract rose before dropping about 41% to 28% on April 18. The April 30 contract has recorded over $16 million in total volume, including nearly $4 million traded during a single session on April 7. The May contract settled near 69% Yes as of April 18 with roughly $1.3 million in volume. A separate market for normalization by the end of June sits at about 81% Yes.

Both Polymarket contracts resolve if IMF Portwatch reports a seven-day moving average of at least 60 ship arrivals covering container, dry bulk, Ro-Ro, general cargo and tanker calls. Before the crisis began in early March, daily transit calls commonly exceeded 60. Since Iranian forces effectively declared the strait closed on March 4, daily vessel counts have fallen to roughly 5–16 ships and the seven-day average has hovered near zero. Kpler data showed eight tankers transited early on April 18 before enforcement resumed, and vessel-tracking services recorded multiple ships executing U-turns near Larak Island.

With about 12 days left before the April 30 deadline, the seven-day average metric presents a timing obstacle: even an immediate full resumption of traffic would make it difficult to reach a 60-ship average in the available window. The April 30 market’s No side stood near 72% on April 18. The April 30 contract resolves as soon as IMF Portwatch publishes qualifying data, or at the contract deadline if no qualifying data appears.

Security conditions remain restrictive. Insurance premiums for vessels attempting Hormuz transit are sharply elevated and many shipping firms have suspended sailings while awaiting clearer guarantees. Pakistan has acted as an intermediary between Washington and Tehran; no formal talks are currently scheduled and no timeline for a broader diplomatic agreement has been announced. Iranian officials described the continued U.S. naval presence at nearby ports as a breach of trust. The White House maintained that the U.S. naval posture will remain in place until a comprehensive agreement is completed.