Countries of the World by Land and Maritime Borders in 90 seconds: with a map
When you type the name of a country all its bordering countries and the country itself will appear: including those with a non-overseas maritime border!
If you want to learn which countries have maritime borders but not land ones, try this quiz
I like this variation on the countries by borders quiz. I got tripped up a few times though because it's really hard to see which of the small island countries you are missing.