Wild swimming is a great way to relax and, especially when the water gets colder, it gives a nice boost to your metabolism and blood circulation.
You may feel cold before you get in the water, but getting out you just feel great and energetic.
You feel your body and therefore you are fully alive.
I find water as an element comforting, always, but compared to taking a shower, in the sea you are wrapped in a large salt water blanket. You have the water tightly around you and all over your body.
It also feels good to regain perspective of how small you are compared to the elements around you.
The Finnish way of sauna is to get hot in the steam, take a dip in the sea or lake, and then repeat. If you have not tried it, it is about time. You will love it.