I bought a Samsung tablet for around $200. Built in gps receiver which is extremely accurate. Takes me right to my slip in the harbour. Navionics app was about $18 I believe. More detail than you will ever use. Plug it in on my boat with a ups adapter. Bought a RAM holder for it and it looks real good. It does have a feature where you can mark your spots when you want. Just have to get used to using it. You can even mark the closure areas by using the "route" feature at home in your leisure. 10 inch screen. Way cheaper than anything else I've looked at. Been using it for over 2 years now and am delighted with it's accuracy and detail and ease of use.