What does the word “spike” mean in this context?

Question

I read a sentence in chapter "The enemy" in my book which was:

The surf beyond the beach was spiked with rocks.

For me, no definition of the word "spike" that I have looked for fits into this context.

Answer 1

This is a past tense of (one meaning of) "spike" as a verb.

• the Oxford Dictionaries lists as a meaning of the verb:

form into or cover with sharp points.

"his hair was matted and spiked with blood"

• Dictionary.com gives, as sense 13:

to provide or set with a spike or spikes.

So

The surf beyond the beach was spiked with rocks.

means that the surf was studded with rocks, or had rocks scattered through it, that stuck up through the water, and probably impeded progress.