He threw up several times during his first boat trip because he was seasick.

seasick 是由 sea（海）和 sick（恶心、不适）组成的复合形容词，字面意思是"因海而感到不适"，即"晕船的"。这种构词方式常见于描述因特定环境引起的不适症状，如 carsick（晕车）、airsick（晕机）等。