The Sportbootführerschein See (SBFS) is a German driving license for pleasure crafts on sea waterways. To get it you have to pass a written and a driving test.
While you should either have experience in driving a boat or visit a course at a boat school to pass the practical test you can easily prepare yourself for the written exam. The test is taken using a known list of multiple choice questions.

This app contains all the questions (except the map tasks) you may be asked in the written exam. Prepare yourself using this App and you will have no problems with the exam.

Note: all the questions you practice are in German language. This is because you also have to take the test in German.