How ro replicate Open Water training in pool, other ways?

So a quick history. I've been a competitive swimmer for most of my life. Outside of stopping for a few years post shoulder surgery when I was about 21, I've always kept it up. I liked swimming in lakes etc, but never competed open water. Older now (61) and my back is really messed up, with nerve issues disc degeneration scoliosis etc, which really put a dent in my ability to swim and cross train. I had severe leg pain due to nerve issues in my back, which I managed with Ai's and CT guided injections. In the past I have always enjoyed open water swimming, when we traveled to the Caribbean etc. Especially if it is choppy or the surf is going. Never competed in OW. I think even as a kid I rarely entered the 1500 free. Still in 2018 I traveled to Brisbane for the Pan Pacific Masters and instead of simply doing in-pool races, I decided to enter the 1K open water on a whim. The first day I went to practice on the beach, the waves and current was so strong, I could not get off the shore. Fast forward a week on competition day the ocean was calmer. Even so two people were taken away by ambulance (one knee, one ankle) from getting smashed by the waves at the start. Even though the waves and current were wicked, I found it exhilarating and loved it. Lucky for me I was able to find a good physio, orthopaedic surgeon, and neurosurgeon. I postponed my surgery until after that competition Shortening the saga, I am almost 5 months post lumbar surgery and doing really well. I am convinced that if it were not for swimming, I would not be as far along in recovery as I am. (did easy flip turns 2 months postop) This past month we traveled to Turks, and thanks to my brand new apple watch, I was able to track my time and distance for the open water swims and swam 2.5-3k almost every other day. I loved it and really challenged myself. I got faster every day but didn't realize how much better in shape I was getting until I got home. When I jumped back in the pool, after only 2 weeks (which was supposed to be a vacation) my Asthma was better, my fitness was better than I have been for probably 6-7 years. SO How do you all replicate that open water feeling and intensity when you train in pool or elsewhere? Do you do anything else, and other fitness work?