There's a kickarse reason all The Block contestants are wearing the same jumper.

If you haven’t been watching with an eagle eye it could have been pretty easy to pass by, but just about every contestant on this season of The Block has been spotted wearing the same hoodie and long-sleeved top this year, and as it happens, there’s an important reason behind it.

It started with Elyse and Josh and quickly moved on to Stick and Wombat. Then we saw Clint donning the jumper, and Jason, and Ronnie. So why are a bunch of rookie renovators all wearing Sea Shepherd tees and jumpers?

According to Wombat, it all came about when the five teams took part in a painting challenge in Williamstown.

"We were down there in a warehouse on the docks in Williamstown and the Steve Irwin [one of Sea Shepherd's biggest vessels] was docked. Josh and I ran over when we had a break and found out more about what they do and got some t-shirts to wear," Wombat tells Mamamia.

Listen: Somehow, The Block is still going strong after nearly 600 episodes. Post continues after audio...

Put simply, Sea Shepherd is an international not-for-profit organisation that works to protect and conserve oceans. From fighting for the Great Barrier Reef to taking on the whaling industry, Sea Shepherd works hard to keep our seas protected and clean, something that spoke deeply to Josh as a keen surfer and Wombat and Sticks, who both live on the central coast.

"I wasn't involved with them in any way before going on the show, but after The Block had finished I had the chance to have a tour of the boat [the Steve Irwin] and I take my hat off to them. Three months on The Block is nothing compared to what they do."

Now you know, it's likely you'll be catching those hoodies and tees on the couples in no time.