John61730 just shared a new project: "Arduino Tide Gauge"
I used an Arduino and a US-100 ultrasonic sensor to make an extremely low-cost tide gauge.
This project measures the tide by sensing the distance to water using a US-100 ultrasonic sensor. The device has a 3D printed base and uses a peanut butter jar to create a waterproof housing. The 3D printed base fits atop a PVC tube which acts as a stilling well to dampen wave effects. Timestamped data is logged to a microSD card while the instantaneous results are displayed on an optional screen or blinked on an LED. The aim of the design was to make an extremely cheap tide gauge so that multiple units could be made which would essentially be disposable.