How to create navigation links from scrollview content

You should use code formatter when you paste code (</> button on the code selection)

struct FishGuideView: View {
    @State var fishes = Fish.fishData
    
    var body: some View {
        VStack {
            Text("Fish Guide")
                .font(.largeTitle)
                .multilineTextAlignment(.center)
                .padding(.horizontal, 2.0)
            
            ScrollView(.horizontal) {
                LazyHStack(spacing: 16.0){
                    ForEach(fishes) { item in
                        VStack {
                            GroupBox {
                                Image(item.fishImage)
                                .resizable()
                                .frame(width: 100, height: 88.0)
                                .clipShape(ContainerRelativeShape())
                            Text(item.fishName)
                                    .font(.caption)
                                    .fontWeight(.semibold)
                                .multilineTextAlignment(.center)
                                .lineLimit(4)
                                .padding(.top)
                            
                            
                        }
                        .frame(width: 150, height: 200.0, alignment: .center)
                                     
                    }
                    }
                    
            } //* -END LAZYVSTACK
        } //* -END SCROLLVIEW
    }
        }
} //* -END STRUCT

You have to embed in navigationView, such as here (take care, I did not test, there may need some minor changes) :

struct FishGuideView: View {
    @State var fishes = Fish.fishData
    
    var body: some View {
        VStack {
            Text("Fish Guide")
                .font(.largeTitle)
                .multilineTextAlignment(.center)
                .padding(.horizontal, 2.0)
            
            NavigationView {
                ScrollView(.horizontal) {
                    LazyHStack(spacing: 16.0){
                        ForEach(fishes) { item in
                            NavigationLink (destination: TheViewToGo()) {  
                            // You have to define the destination view you want to go for each item. 
                            // Note it would be more readable to change item in fish.
                                VStack {
                                    GroupBox {
                                        Image(item.fishImage)
                                            .resizable()
                                            .frame(width: 100, height: 88.0)
                                            .clipShape(ContainerRelativeShape())
                                        Text(item.fishName)
                                            .font(.caption)
                                            .fontWeight(.semibold)
                                            .multilineTextAlignment(.center)
                                            .lineLimit(4)
                                            .padding(.top)
                                        
                                        
                                    }
                                    .frame(width: 150, height: 200.0, alignment: .center)
                                    
                                }
                            }
                        }.navigationTitle("Title")
                        
                    } //* -END LAZYVSTACK
                } //* -END SCROLLVIEW
            }
        }
    }
} //* -END STRUCT