Swim Sprints

Can anyone give me a good example of a HIIT-type program for swimming? I haven’t swam properly in years and did several laps recently which I found tremendously difficult. On a positive note I was pleasantly surprised at how much my upper body blew up and the tightness through my core tells me I’m working muscles differently than normal.

Just looking for an additional option in my cardio repertoire.
Cheers J.

Sprint a lap. Rest ~30 sec. repeat.