I'm assuming MorCal is calcium (which you really didn't need but that's another topic). If so, you can swim immediately.
Our normal recommendation is to wait 30 mins to an hour after adding chems for anything except cyanuric acid and you can swim while that's dissolving in the pool.
The only time calcium is an issue in vinyl lined pools is if it gets too high it can cause scaling or if there is any stone or concrete material touching the water.
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