What image does the line "The wrinkled sea beneath him crawls" from "The Eagle" convey to you?

"The wrinkled sea" could be a wonderfully imaginative description of the peaks and valleys formed by the waves below the eagle's viewpoint as the tide "crawls" in and out along the shoreline. Particularly large wrinkles would be trimmed in foamy white as the sea crashes against itself or against the rocks on the shore.

Since the eagle is watching from a vantage point on "mountain walls," it is possible that the water is clear enough to see to the bottom of the sea in that area, so the wrinkles could be uneven rocks below the surface of the water. They might be broken up and jagged, might be folded into creases by the movement and formation of the earth's crust, or they may be worn into smooth contours by the action of the waves over many years.

Does the line "The wrinkled sea beneath him crawls" reveal the eagle's pride?

Individual readers are going to interpret this line differently. For me personally, no, I do not think "the wrinkled sea beneath him crawls" shows the eagle's pride.

On one hand, the line is very literal. The eagle is a soaring bird with great vision. It is capable of flying quite high with minimal effort. Its vision allows it to scan and spot targets from a great distance away. When you are far away from something, it appears to barely move. Think of a road trip. The trees along the roadside blur past your car, but the mountains in the distance barely appear to move at all. If you've ever had a window seat on an airplane, you've seen the same effect. The plane might be moving hundreds of miles per hour; however, the ground beneath you appears to slowly inch by. This is what the line in the poem is indicating. The eagle is very high up, and the ocean appears to crawl by. Additionally, we know the eagle is high up because the great waves of the ocean appear to be merely wrinkles.

If I'm forced to find additional meaning from the line, I think it shows the eagle acting from a place of privilege. This doesn't automatically equate to pridefulness. Rulers and kings are usually seated at a place of elevation, or they have a castle on the hill. Being higher than someone else usually connotes power and privilege. The eagle is in a powerful and privileged position, which is why it is such an effective predator, but again, that doesn't necessarily mean prideful.