The writer acknowledges that all of this creation is beyond our ability to fully grasp and there must be a God who created all of this in first place.
 So is this great and wide sea, wherein are things creeping innumerable, both small and great beasts.
 There go the ships: there is that leviathan, whom Thou hast made to play therein.
We now turn to oceanic life. Ocean life was created on the fifth day of the creation story. Genesis 1:21-22 says, And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good. And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth. There is a great variety of oceans species. I suspect the psalmist knew the fact that the ocean is full of creatures beyond numbering.
The reference to the “ships” in verse 26 reminds us that a purpose of seas is to allow relatively fast travel from one point of land to another. Again, the issue is about appreciating God's creation as it is and how we are blessed by this world He created.
Finally a quick word on the word "leviathan" in verse 26. This word is mentioned five times in the Old Testament and apparently refers to some type of giant (probably extinct) sea creature. The purpose of mentioning this sea animal, whatever it was, is that if people were not be capable of stopping this creature by themselves, God is more powerful than any and all creatures in the sea. He “balances” the amount of life in the sea so that ships can still travel along its surface without the threat of this animal.