Is it permissible for one who is not in a state of major ritual impurity (ghusl is not required for him) to perform ablution (wudu') by throwing himself into the sea, and if it is not permissible, must he repeat the prayer, or is he excused due to his ignorance despite his ability to learn and his negligence in doing so?

It is not permissible to perform ablution (wudu') by immersion in the sea, due to the lack of order among the limbs of ablution, which is a fundamental condition for its validity. However, ritual bathing (ghusl) by immersion is permissible with the intention, rinsing the mouth, and sniffing water into the nose, because order is not a condition for it.

Therefore, if one intending to perform ablution immerses himself in water with the intention of ablution, then emerges and arranges his limbs, it is sufficient for him. As for someone who, out of ignorance, thought his ablution by immersion was valid, he is not required to repeat past prayers performed with that purification, because his ignorance is excused.