How I got from an Open Water course via GUE Fundamentals to sidemount instructor is on the blog: Something Was Missing: From Open Water to a Sidewinder.
I have logged many thousands of dives in cold water in Germany (lakes and mines), in warmer waters (Malta, Gozo, Croatia) and above all in the cenotes of Mexico, where I did my cave training up to Full Cave and Cave CCR. I have logged several hundred hours on the KISS Sidewinder since 2021 and dive sidemount (OC) and backmount doubles in my own time. My own technical training was with GUE, TDI, ISE and PSAI. That experience feeds into my teaching; I do not teach cave courses.

As an instructor I take you through GUE courses from Performance Diver via Fundamentals and primers to DPV 1, and through the sidemount courses under SDI and TDI up to Intro to Tech and Decompression Procedures. Every course has its own page, and all of them are listed on the home page under sidemount and GUE.

Several days a month I am at Deepstop in Schwetzingen, where I advise customers in the shop, am the contact for sidemount systems and set them up. Deepstop is also the base for my courses: theory in the training room, with the local lakes a short drive away.
