Sob esta licença https://assetstore.unity.com/packages/3d/vehicles/sea/boat-game-kit-barco-navega... You can use it in your project however you wish; there is no need to provide credit (though you may do so if you like). However, you are not permitted to sell the project separately as if it were your own creation. Apart from that, you are free to use or modify it however you prefer.