Tides via Stormglass.io

If you want to use the tides feature on a watchface using stormglass as a provider, you need to register on their website to retrieve an API Key which you can enter in the specific field in your watchface settings.
https://stormglass.io/
When you copy your APIkey from anywhere make sure that all characters are included (usually over 60) - sometimes Android/IOS cuts away a part after a "-".
The free (stormglass io) plan features 10 free requests a day which is enough to provide tide data to supported TitanicTurtle watchfaces.
(If your watchface supports stormglass io as a weather provider and you plan to use it, you might need another subscription plan)

Usually, tide data is being downloaded for multiple days and refreshed every day if there is a phone connection available. So even if you do not have an internet connection expect the tide data to be displayed at least for 3 (Horizon) / 5 (Centurion) days. (depends on the watchface / device)
As soon as you have entered the stormglass io API key in the settings, it might take up to 30 minutes until the data is being downloaded and available.
If you change your position be sure to get a gps signal on your watch so that the tide data can be updated for the new location.

Make sure your watch is connected via bluetooth to your phone where the Connect App (not Connect IQ) is at least running in the background.
If you see a message like "GPS?" on your watch, do a gps fix so that the watchface knows your position. (Get in the starting screen of an activity like "Running" and wait until your watch got a gps signal)