File this under "reasons cruising Down Under keeps us humble." Just four days before departure, Carnival Cruise Line told guests aboard Carnival Encounter that its September 5 sailing out of Brisbane would be quietly rerouting, because the water on the way into Cairns has gotten too shallow to squeeze a 108,865-ton ship through safely.

The original 6-night Great Barrier Reef itinerary had Willis Island on September 7, Cairns on the 8th, and Airlie Beach on the 9th. Now Cairns is off the board entirely. In its place, Airlie Beach jumps up a day to September 8, and a brand-new call at Townsville lands on September 9. Willis Island survives the reshuffle untouched.

Carnival's notice didn't mince words: "Current channel depths have reduced and are now too shallow to allow for the safe passage of our ship to Cairns Cruise Terminal, and the issue will not be fixed before our planned visit." Translation: the reef isn't the only thing that's shallow this week.

As itinerary changes go, the damage is mild. Guests get back to Brisbane one hour later than planned — 8 a.m. instead of 7 on September 11 — and every prepaid Cairns excursion is automatically refunded. New Townsville excursions can be booked once you're onboard via the HUB app or the Carnival Adventures Desk. No word yet on help for anyone whose post-cruise flight now looks a little tight.

Tim, this one's for you

Our favorite Australian SpeakPipe correspondent is going to have thoughts, and we want them. If you've sailed out of Brisbane lately, tell us how the Encounter's Aussie itineraries are holding up — the ship is based Down Under through 2027 and 2028, so this won't be the last time a tide chart rewrites someone's vacation.

The good news: Carnival says Encounter is still scheduled back at Cairns on a September 26 sailing, with an overnight call beginning September 29. Assuming, of course, the channel remembers how to be a channel by then.