The sonar float in "Stardew Valley" is a very important special equipment in the game, and the specific function of the sonar float is to display the type of fish you caught before you retract the fishing line. With this information, you can decide whether the fish is worth the effort to catch.
What is the use of sonar floats in Stardew Valley
This clever piece of fishing gear acts like a mini fish finder, showing you the type of fish you're catching before you reel in your line. With this information, you can decide whether the fish is worth the effort, or give up on the hunt and focus on finding your true target.
If you plan to use it to catch some rare fish, it is recommended to use it with curiosity bait. However, you need to have an "Advanced Iridium Fishing Rod" to use both equipment at the same time.