The first time I went to the ocean with my family.
I always remember the first time I went to the ocean with my family.
この場合、次のように答えることができます。
ーThe first time I went to the ocean with my family.
「家族で初めて海に言った時です」
ーI always remember the first time I went to the ocean with my family.
「家族と初めて海へ行った時のことをいつも思い出します」
例:
The first time I went to the ocean with my family is one of my favourite memories from my childhood.
「家族で初めて海に行ったのが、子供の頃のお気に入りの思い出の一つです」
ご参考まで!