1. On the occasions when they have pushed to shore an unconscious human being they have much more likely done it out of curiosity or for sport, as in riding the bow waves of a ship.
On the occasions when 在……条件下
out of curiosity 出于好奇心
I believe Wang Lin was just acting out of curiosity.
我觉得王林这样做只是出于好奇。
2. If, as has been reported, they have protected humans from sharks, it may have been because curiosity attracted them and because the scent of a possible meal attracted the sharks.
may have been 对过去发生的事情表示猜测。
3. It is possible that upon such an occasion a battle ensued, with the sharks being driven away or killed.
It在这里是形式主语，真正的主语是后面that引导的从句。with后面通常加过去分词或现在分词表示伴随状语。
4. They are constantly after the turtles, who peacefully submit to all sorts of indignities.
submit to 使服从，使受到，服从，忍受，顺从
The heroic people will never submit to foreign rule.
英雄的人民决不会屈服于外国的统治。
5. He no sooner recovers his equilibrium than the next porpoise comes along and hits him another crack.
no sooner than 一……就
