Nautical map download?

Hi all, I’ve explored almost all of the features the inReach has to offer, and have looked into the various map types offered and regions, but one thing gets me that I cannot figure out. How do they have topographical maps of mountains and hiking trails, but no readily accessible nautical maps to where it could be used offshore or inshore as a stand-alone item? I understand once you pair it with the Earthmate app you can use it, but if you absolutely had to use it to navigate via boat home say at night and your phones dead, it shows you very, very little. Let alone setting dive spots before a day trip out and relying on it to the spot and back! If they offer nautical maps and I have not found it, could someone point me in the right direction? Thank you!