He submerges his anger and continues the conversation politely.

submerges 是动词 submerge 的第三人称单数形式。submerge 由前缀 sub-（表示"在...下面"）和词根 merge（"浸入、合并"）组成，字面意思是"浸入水下"，引申为"压抑、隐藏（情绪等）"。