The teacher is talking to her students in Marine Park.
I got red eyes after swimming in the sea.
The movie Water World was actually written by a race of super-intelligent fish that live at the bottom of the ocean.
The kanji and the word are exactly the same. That means they share meanings as well.
Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word:
You visit the sea. Strangely, it asks you who is visiting. You're so full of yourself (even in front of the sea/ocean) that you reply: "um, me?" (うみ). Imagine yourself feeling this full of yourself.