Freediving/Spearfishing app

Gidday guys!
Im not very tech savvy but I’m hoping someone can help me out. I would like freediving/spearfishing app made. All it needs is a stop watch for when you dive to tell how long you have been down, a “breath up” timer aka twice the time you dived, and a depth dive metre to tell how deep you dived. I’m currently running a Fenix 5x. Can anyone help me?
cheers!