ViewModifier version to create the aqua effect

AquaButtonViewModifier.swift

private struct AquaButtonViewModifier: ViewModifier {
    let color: Color
    //Content type is inferred from the View this is trying to modify
    func body(content: Content) -> some View {
        content
            // adding a gradient background based on the color used in the parameter
            .background(LinearGradient(gradient: Gradient(colors: [.white, color.opacity(0.6), .white]), startPoint: .top, endPoint: .bottom))
            // rounded corners
            .cornerRadius(12)
            // adding the borders using overlay with a RoundedRectangle
            .overlay(RoundedRectangle(cornerRadius: 12)
                        .stroke(color, lineWidth: 2.0))
            // a shadow to give more effect
            .shadow(color: color, radius: 6, x: 0.0, y: 6.0)
    }
}

// Using extension make it easy to access
// and also you can define the default parameters
extension View {
    func aqua(color: Color = .blue) -> some View {
        modifier(AquaButtonViewModifier(color: color))
    }
}

struct AquaButtonViewModifier_Previews: PreviewProvider {
    static var previews: some View {
        Text("My button")
            .foregroundColor(.white)
            .padding()
            .aqua(color: .blue) // Here is the modifier
    }
}