If the tide is raising water, then it is raising the ship on water, too. So water will reach still the first rung.
Tricky little question. The boat floats and will rise and fall with the tide, So the water will never reach higher than the bottom rung.
It never will reach the "Seventh" rung on the ladder because the ship will rise with the tidal influx. In order to make the ship lower into the water, weight will have to be added like on a cargo ship. Then if that's the case, It's how quickly the ship is being loaded.