Because I was not satisfied with the information about the water temperature of the Baltic Sea during a past vacation stay, I built a thermometer with M5Stack components and a remote temperature sensor and presented it in a blog post. With the remote DS18B20 temperature sensor, I measured the water temperature at a depth of one meter.
Now the vacations are approaching again, and the message from the BSH still shows very cool water at the end of May.
I have extended the presented thermometer to follow the water temperature changes and be immune from bigger surprises.
Because of the slightly larger display, I replaced the M5StickC with an M5StickC+ and used an M5StickC 18650C to increase the battery capacity. In addition, the thermometer is much easier to handle.
To have the readings available on my mobile phone, I use it as a mobile hotspot and send the readings from the M5StickC+ via WiFi to the mobile phone, which then sends the data to the Pushover server. From there, the data is then distributed to the selected end devices.
This setup won't affect the water temperature, but I can record it in writing. And if it stays that cold, then I can document my heroism.

That's really impressive! Building your own thermometer to monitor the Baltic Sea's water temperature is a unique approach. Upgrading to the M5StickC+ with an M5StickC 18650C for more battery capacity sounds like a smart move. And the data transmission setup using your mobile phone as a hotspot and Pushover server is clever! It may not change the water temperature, but it's great for keeping records. Thanks for sharing, and here's the temperature converter link you mentioned: temperature converter. Good luck with your upcoming vacation and documenting your heroism! 😄🌊🌡️