The Optode Team Austria (OTA) is a group of leading researchers in the field of optical chemicals sensors formed by members of the Institute of Analytical Chemistry and Food Chemistry at Graz University of Technology (Austria) and the company PyroScience GmbH (Germany).  OTA is the only landlocked team participating in the Wendy Schmidt Ocean Health XPrize competition, but with more than 15 years of experience in developing analytical equipment for marine research and the involvement in several marine research project OTA has the expertise required to participate.  The focus of research is the accurate, long time stable measurement of pH using optical sensors. The major part of work contributed to develop a device for the XPrize competition was done voluntarily after working hours by the developers, researchers and PhD students of the OTA.