iPhone SE is it waterproof

No iPhone has ever been marketed as waterproof. While apple markets newer models as water resistant, they also warn against any and all contact with water. Damage by water is not covered by warranty.

dunno about it being waterproof, but it is water resistant.

would highly recommend a life proof case, or “waterproof”

Yes, Rated IP67 (maximum depth of 1 metre up to 30 minutes) under IEC standard 60529