Coins are one of the currencies available in Fishing Clash. You need them to upgrade Lures and progress in the game. You may also use Coins to buy specific Lures or Skill Tree Tokens from the Shop.
Coins play a key role in the Gold Rush Events, where you use Coins to clear the Event thresholds and receive them back as rewards! This Event is not the only one with Coins as rewards, as there are plenty more! Be sure to participate in these when your coffers are getting low on Coins!
If you still need some more Coins, remember that you get them for catching fish – for the first 50 fish caught every day, for Championships, and for Duels (for a maximum of 15 Duels a day). The number of daily Coins available through fishing can be increased along with your VIP level. Additionally, bundles of Coins can be bought directly in the Shop, and these can be found in the "Coins" category.