Wearing semi transparent clothing

Q:  Some of my clothes are only see-through when looked at closely. The skin can only be seen underneath if there is enough light and if I look very closely but to an onlooker from afar, they would not be able to see my skin. Am I allowed to wear such clothes during Namaaz, which are opaque and not transparent but only see-through from a near distance?

Repentance

Q: I would like to ask the following question on repentance

1. Does repentance wipe out previous sins?

2. Am I always obliged to confess to the one whom I've wronged even if this might bring severe enmity?

3. How do I feel regret during repenting?

Diving in Islam

Q: Is diving permissible in Islam? If one goes diving with the intention of fulfilling the sunnah of swimming, will this be allowed?

Someone told me that it is impermissible because there is fire under the ocean according to a Hadith. If that is the case then how did the Sahaabah learn how to swim since they did not have swimming pools like how we have today?