Map/Plotting Apps

Question for the group.  Very new to Forums and this stuff, and only a few years into Kayak crabbing and only 1 season for kayak fishing in the bag.  That being said, I was wondering if there is an app/program that ya'll use to plot, pin, and make notes on said pins for fishing/crabbing.  I have had varying degrees of success these past few season, and want to start compiling (with the help of another friend/kayak crabber) all of our info on a master map that we can both update and share our data including time of day/tide/depth ect.  I'm sure this is probably old hat for a lot on the forum, and searched around a bit with no luck so far.  I'm looking for something I can download on an Iphone without having to buy a dedicated unit quite yet.  Thanks for the input and great amount of info that I've already pulled from this site.

I have the navionics app downloaded to my Iphone and Ipad. It works pretty good. Check it out.