Maritime Boundaries follow the link below. Consider using the Shape files from this link to create a custom GIS map.
Here is a link for the US (and a few other countries) nautical charts provided by NOAA. Click the image below.
Some charts can be seen directly from the sites listed below and other charts must be downloaded and opened using free software like OpenCPN. Open CPN is a chart plotter and GPS navigation software you can use to upload your nautical charts. These uploaded charts should only be used for a reference (getting an idea for the area). They can not be guaranteed to be perfectly accurate (like most other maps). Here is the link for Open CPN Free download http://opencpn.org/ocpn/.
Below are links for countries that provide some free nautical chart downloads and free images that can be seen directly from their websites.
South China Sea- http://scsenc.eahc.asia/main.php
Czech Republic- http://www.lavdis.cz/index.php?pg=46&ln=cz