That was the first time I ever went scuba diving in my life!
どちらも「人生で初めてスキューバダイビングをしました！」という言い方です。
1) That was my first time scuba diving ever!
2) That was the first time I ever went scuba diving in my life!
ダイビングはスキューバダイビングのことですよね？
ちなみにスキューバのSCUBAは
self‐contained underwater breathing apparatus (自給式水中呼吸装置)の頭文字を取っています。
ご参考になれば幸いです！
I tried diving for the first time this year! It was my first time
I gave diving a go for the first time ever! It was a new life experience!
今年 - this year
初めて - first time, new
ダイビング - diving
挑戦 - challenge, attempted
人生 - life, lifetime
体験 - experience
人生の初めての体験 - first time in my life, new life experience
〜〜を挑戦しましたはchallengeを使わなくて大丈夫です、tryやgave a goで大丈夫です
I tried diving for the first time this year! It was my first time
I gave diving a go for the first time ever! It was a new life experience!
日本 
イギリス 
