SEAiq is what I consider to be the only real navigation app around for iOS. The chart tool functionality (multiple EBLs, VRMs, and other markup functions) mean you can, if needed, perform similar operations that you might be used to on paper charts. I’ve added danger bearings, marked out anchorage areas, even plotted a running fix with it. (That last just involved creative use of a handful of EBLs.)The AIS functionality is also incredibly useful; the course vectors and rate of turn indicators make it very easy to visualize crossing situations. Also useful is the ability to attach a VRM or EBL to AIS targets.If you’re in the US you have free future access to all the official NOAA charts, and the tiling is handled reasonably well. I’ve also loaded New Zealand ENC charts as well as purchased others from Chartworld.My workflow involves planning and plotting on the laptop, then transferring the files to phone and iPad for reference underway. I see the same notes on every device. What could be improved is the overall app speed, and being able to use purchased charts across devices (I know that last is more a problem of the chart suppliers).