Making it easier to explore our waterways than ever before

The foundation is the official Maritime Safety Queensland predictions for the Gold Coast Seaway — the reference port for this coast — published as 10-minute-interval tables plus exact high/low times on Queensland's open data portal. All heights are in metres above LAT (Lowest Astronomical Tide, the Queensland Port Datum) — the same datum as the depths on the charts.

The tide inside the Broadwater is not the tide at the Seaway: the further you are from the entrance, the later and generally smaller the tide. So the cruising ground is divided into 26 tide zones (Sanctuary Cove, Paradise Point, Tipplers, Jacobs Well…), each carrying the official MSQ Queensland Tide Tables secondary-place corrections: separate time shifts for high and low water, plus a height ratio and offset. Highs and lows move by their own offsets — which means the flood and ebb durations stretch or shrink — so the engine re-maps every moment to the equivalent phase of the Seaway curve before scaling the height. Wherever you are on the map, you get the nearest zone's curve, not a number copied from the Seaway.

Tide tables are astronomical predictions — sun, moon and coastline. Real water also feels wind setup, barometric pressure and storm surge. Every 10 minutes the engine reads Queensland's near-real-time storm-tide gauge at the Seaway and takes the difference between what the gauge measures and what the tables predicted. That live residual is added to your zone's prediction, so "Height now" reflects the water that is actually under you — during a blow it can differ from the tables by well over a decimetre.

The travel windows are scanned in 10-minute steps across the tide zones around you. A moment is excluded when any of these is true:

• Night — outside first light to last light (with a 15-minute evening buffer). Sunrise and dusk are computed for your exact position.
• Stranding risk — if you grounded at that moment on a falling tide, the water would not return to the same level within 6 hours.
• Dark refloat — the water would come back, but only after dark.
• Top of tide — the level is within 0.15 m of the top of the current tidal cycle, so a grounding there has almost no rising water left to lift you off.
• Local hazards — named shallow spots carry their own rules: the Coomera North Arm mouth, Whalleys Gutter and McKenzies Channel are flagged whenever the level is below 0.3 m Seaway-equivalent, rising or falling.

Window edges are deliberately rounded toward caution, and the same tide always produces the same windows, no matter when you ask.

When you tell the map you've touched bottom, the level at that moment in your tide zone becomes your refloat threshold — by definition, that's exactly the water you need back. The engine then walks the tide curve forward in 5-minute steps (up to 28 days if it has to) to find every window when the water regains that level.

It also reports the margin: how far the lifting tide's peak rises above your threshold. Margins under about 0.15 m are flagged as not dependable — weather can shift the real level by that much — and the app only calls it "good news" when at least 0.2 m of rise is still to come. If the boat drove up onto a shallower bank, the engine can be asked for extra water above the grounding level, which pushes the refloat time later and is exactly why "reverse off the way you came" is the golden rule.