Modify swiftui back button

I am trying to modify swiftui back button by giving it different word and color. But an extra back button still appear even i did not include it.
How can i get rid of it and make my cancel button does the navigate back like the original back button?

extra button appear

 import SwiftUI

struct ContentView: View {
 var body: some View {
    NavigationView {
        NavigationLink(destination: SeaView()) {
            Text("SeaView")
        }
    }
  }
}

struct SeaView: View {
 var body: some View {
    List {
        Text("Fish")
        Text("Octopus")
        Text("Shark")
    }
    .toolbar {
        ToolbarItem(placement: .navigationBarLeading) {
            Button("Cancel") {
                
            }.foregroundColor(Color.red)
        }
    }
  }
}

>Solution :

Hide default one explicitly, like

List {
    Text("Fish")
    Text("Octopus")
    Text("Shark")
}
.navigationBarBackButtonHidden(true)   // << here !!