I'd like to add that I never use plain oil in dry hair. I always use it in either wet or damp (misted) hair.
As for swimming, I first wet my hair with plain water, then add a moisturizing conditioner with natural oils in it and put my hair in a braid and/or up. If you don't have a condish containing oils, you can add them yourself.
A sort of DT while you're swimming
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