Overseas, Foreign, Abroad
noun, の adjective
The outside of the sea is someplace overseas. It can also be foreign or abroad if those words are easier to remember for you.
かいがい
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
海外に行きたいなぁ。
I want to go abroad.
一人で海外に行ったことはない。
I have never been abroad alone.
このスペース、海外のホテルみたいですね。
This space looks like a hotel overseas.