Half seas over is a colloquial expression that refers to the state of being drunk or intoxicated. Some suitable antonyms for this phrase include sober, clear-headed, abstinent, lucid, and moderate. These words suggest a state of mental and physical alertness, free from the effects of alcohol or drugs. People who are sober or clear-headed are fully aware of their surroundings and able to make sound judgments. On the other hand, those who are half seas over may have impaired judgment, slurred speech, and difficulty walking. Therefore, it is important to exercise moderation and restraint when consuming alcohol or any other substance that can impair judgment and lead to dangerous situations.