(Ship horn blasts) - Where are we going to?

- [RUSSELL CUHEL] The wreck.

Now, let's see.

3.3, nautical miles.

(water swirling) - Now we are just outside of the main gap.

This is the main gap, between the Milwaukee Harbor and Lake Michigan.

Our goal is to Pris Willem, which is about three nautical miles off shore.

And, we'll be sampling every mile on the way out.

- [CARMEN AGUILAR] So, the Secchi gave us what?

10.5, no!

9.

- 10.4... (indistinct) 9 and the other side.

- The other side is 6.7.

- 6.7.

So, the quagga mussels started invading in Lake Michigan around 2003, in a substantial rate.

And, when you see the shipwreck you'll start noticing that in between the mussels, now you can have algae.

So, the algae are gonna be also attaching to there, and what happens is that you have organic matter now depositing into your shipwreck and start degrading it as well.

So, very slowly but you start changing the characteristics of the surfaces.

- Three, two, one sample 12, 10, 50, number 10.

Now we're going to deploy a remotely operated vehicle or ROV that we will use to collect samples from the bottom.

We'll also use it to survey the shipwreck and see what kinds of changes have occurred Since last time we were here.

(water swirling) Here, we are looking at the edge of the Prins Willem and, we're near a railing and you can see that the surfaces are largely encrusted with a growth, which is mostly mussels.

There are several ways in which the animals alter the shipwrecks.

And, in the case of a shipwreck any alteration is permanent.

Stress by current, for example during a storm and pulled off, they will pull a small piece of wood along With them.

Most of the shipwrecks in Lake Michigan are completely covered with quagga mussels.

And, that is really causing the breakdown of the shipwrecks, it's become accelerated.

(underwater drone sounds) Really, our understanding of those ships also develops over time.

As new technology becomes available to us.

We try to use that to really understand how these ships are.

To monitor their status, and then also to protect them for future generations to come visit and enjoy.