Garmin Forerunner 935 - need advice on pool training intervals

Hi everyone, just received a Forerunner 935 as a gift and I'm not really sure how to set my swim training intervals.

I would like to set it at 20 repetitions of 1m.39s training interval, with 7s rest interval. 50m pool if this matters.

The only interval training I see in the running menu, but this only goes in 5s increments. I don't need any other swimming data, just the time intervals above. Any advice?