I was at the sea once in my life. I was swimming there and I dived maybe 2-3 meters deep. So that was my lowest point in my life.
I also got terrible sunburn there. My pale skin doesn't mate with sun very well.
But apart from this silly response? IDK, I was apparently pretty fortunate in my life so far. Sure there were ups and downs, some minor, some major. The lowest I can think of was probably before my college final exams. I wasn't the best student and these major exams were pretty damn difficult. Trying to squeeze everything in my head was very, very stressful to the point I felt I was going a bit crazy.