A couple of years ago, while in a friend’s boat in the Charleston harbor, I noticed something that demanded further investigation.

From a distance, I could see a man wading near a sandbar. It appeared he had tethered his boat to his waist as he walked through the salty shallows.

The modest boat had two pieces of plywood projecting from either side. As the man walked ahead of the boat, he was constantly reaching below the surface and tossing something into his boat. At times, he’d come up with something in each hand.

This continued for a period of time. It became clear that the plywood was positioned to prevent whatever was piling up in the boat from spilling overboard.

I watched for more than 45 minutes until I just had to know more. I suggested to my friend we venture to a little closer.

By the way, I’ve never owned a boat, though I’ve lived around water most of my life. I subscribe to the notion that it’s not necessary to own a boat as long as you have a friend or two that do. It’s even better if that friend who has the boat also shares a common curiosity about such matters.

Anyway, so here’s the deal. What I was watching was a horseshoe crab harvest.

This creature is ancient. It’s been around more than half a billion years.

But why would someone be hauling every horseshoe crab it could find into his boat? Where is he taking them and what happens when they get there?

If those questions popped into your mind too, then you’re just the kind of person with whom I’d want to share a boat ride.

Blue bloods

As it turns out, the blood of a horseshoe crab is valuable. How valuable? How does $15,000 a quart strike you?

A horseshoe crab’s blood is in high demand because it is used to screen every drug, implant and medical device before it is used in humans.

In short, it’s used to test for bacterial contamination. The blood, which is baby blue in color, saves countless human lives every year.

There are a handful of labs in the country that collect this blood and one of those is located in Charleston.

Generally, in the space of 72 hours, the crab is captured, transported, cleaned, sterilized, bled and then returned back to the ocean.

Approximately 200 to 400 milliliters of the blood are taken and research indicates anywhere from 6 percent to 30 percent of the creatures die in the process.

Amy Fowler, a marine scientist at the Fort Johnson Marine Research Institute, says any person to ever receive a flu or polio vaccine or undergo any surgery owes their life to a horseshoe crab.

A living fossil

Horseshoe crabs belong to the arthropod group, as in spiders and scorpions.

In mid-April through the month of May, these creatures will once again make their way to our waters for their mating season.

They play a part in our ecosystem as well.

There are 13 different migratory birds that feed on horseshoe crab eggs. The red knot, for instance, makes a 30,000-mile trip from Brazil to the Arctic and depends on the eggs to fuel that journey.

So if you’ve ever looked at a horseshoe crab and judged it by its looks, you’ve totally missed the boat.

They suggest there’s a greater lesson: that there’s an overriding purpose for all of God’s creatures. It’s hard to believe we’re all here by accident.

Reach Warren Peper at peperwarren@gmail.