海牛的行为动作: swim,roll,do somersaults,migrate,breathepush, sleep, rest, float 海牛进食的动作: nibble,graze, munch,eat, grind,drink,swallow 海牛的外貌特征: gray,wrinkled,mighty,big,heavy,large 海牛的身体结构: whisker, skin, tail, eye,nostril,flipper, lip,molar 与海牛的生活习性有关的词: mammal,super swimmer,shallowwater, ocean, river, warm water, herbivore, near the surface be similar to...与......相似 teach sb.how to do sth.教某人怎样做某事 take a breath 吸气 on one'sown 靠自己的力量，独自地 atatime每次 定语从句: Manatees are mammals that live in the water. 比较状语从句: That's as long as two kids'bikes lined up endtoend. 被动语态:Amanatee baby is called a calf 动名词短语作主语: Swallowing trash can hurt manatees 结果状语从句: Fishing line can get tangled around manatees sothey can't swim.