I’ve just come across a tidal app in an old issue of Yachting Monthly called ‘Tides Planner’ by Imray, the chart people. It shows the tidal curve for both standard and secondary ports and allows you to set parameters for minimum depth etc. The free version allows users to access tides for the next 7 days or you can pay £3.99 for a year’s tides. You can also get tidal flow charts for a further payment. I’ve set my parameters to the depth of water over chart datum required to leave and enter the inner harbour where I keep my boat. Apparently internet connection isn’t required as all the data is downloaded with the app and stored on the device.