1to struggle in water and be unable to breathe; to sink below the surface; to (nearly) drown
海で溺れている人を見つけて助けた。
I found someone drowning in the sea and rescued them.
泳げない子どもが川で溺れかけた。
A child who couldn't swim nearly drowned in the river.
溺れている人を見つけたら、まず大声で助けを呼びましょう。
If you see someone drowning, first shout loudly for help.
2to be so absorbed in something that one loses self-control; to indulge in or become addicted to something (e.g. alcohol, pleasure, emotion) — used figuratively
彼は若い頃、酒に溺れて仕事を失った。
When he was young, he became addicted to alcohol and lost his job.
彼女は恋愛に溺れて、周りが見えなくなっていた。
She was so absorbed in the relationship that she couldn't see anything else.
ゲームに溺れて夜更かしが続くと、体調を崩しますよ。
If you keep getting absorbed in games and staying up late, you'll wreck your health.