The National Oceanic and Atmospheric Administration (NOAA) provides electronic navigational charts.

The Navionics Boating app itself is free to download from the Apple App Store or Google Play Store , but it does not come with permanent free charts.

Garmin is currently testing a model where is free to record, but uploading your data to the cloud (to download other people's data) requires a subscription.

A community-driven project that offers basic marine charts for kayaking and small lake fishing.

If you want completely free marine charts without a subscription: NOAA Vector Charts