1, the sea cucumber relies on muscle stretching and crawling, and can only advance four meters per hour.

2, the barracuda can swim thousands of meters per hour, attacking other animals faster than an ordinary train.

3, squid and octopus can suddenly spray water in front of them, using the counter-thrust of the water to quickly retreat.

4, deep-water fish themselves have luminous organs, swimming like twinkling stars.

5, the elasmobranch body length of 10 centimeters or so, the gill cavity is very large, the gill cover seal, can store a lot of air. Skin covered with blood vessels, can be directly with the air for gas exchange. The caudal fin is also an auxiliary respiratory organ.