Apple Watch Ultra doesn't split pool swim workouts

i recently got the apple watch ultra. i played around with the action button and saw that it can split workouts, but not pool swims? i also find it irritating that it can’t split workouts if have it set to just open the workouts app, it has to be starting a specific workout, even though i back out and start another. does anyone have any tips?

[Re-Titled by Moderator]

Original Title: starting splits in pool swims