Six weeks ago, a mysterious sea monster with purple tentacles studded with lime green suckers emerged from the windows of Building 611 at the Navy Yard. It immediately drew attention because of its sheer size — the 30-feet-long tentacles could be seen from the air on flights into Philadelphia.

The inflatable art installation, which took four days to install in late September, is the first project of Group X, an anonymous art collective based in Philly. The group commissioned U.K. street art duo Luke Egan and Pete Hamilton — also known as Filthy Luker and Pedro Estrellas — to design the sea monster, which will be officially taken down Friday evening.

We chatted with Egan, who is in town to bid goodbye to one of the largest installations of tentacles he's ever done.

What are some of your favorite responses to this artwork?

There was someone who came here and they were really upset that they weren't allowed in the building to see the rest of the octopus. That was a big win for us, you know? They really believed that there was an octopus hanging out in the building. That's the illusion.

It's like a big visual joke taken a little too far, basically.

Philadelphia has really embraced the piece on the whole, though. I'm constantly getting Instagram comments from people asking if we can leave it in the city because this is the coolest thing they've seen. It's a huge compliment, given the amount of art that's here.

How did you get started in making inflatables for street art?

We've been making inflatables for about 23 years, and in that time we've done a lot of experimentation.

We used to design stuff without the use of any computers, just using math and geometry. We really got to know what can be achieved with inflatable sculptures.

We would do things like take apart a toilet roll to figure out how to get a spiral seam or play with crude forms of origami. There's no notebook on how to make inflatables, so we had to learn everything ourselves.

We used to take our inflatables to parks or into the street to inflate them, and we got a kick out of the conversations we'd have with people just walking by, so we started to make sculptures just for use in the street.

Why tentacles?

The tentacles are great shapes for inflatables to be, with beautiful curves and how they become completely animated in the wind.

In designing these pieces, the very first ones were knocked up in an afternoon in Bristol [England] for an exhibit in a friend's front room. I thought it'd be funny to make it look like an octopus had moved in, and from there, the tentacles became bigger and bigger, and we began installing them in different places around the world after that.

Part of the illusion and the visual joke we're creating is that the installation requires the audience to use their imaginations to piece together the blank spaces, like, "There's an octopus in the building!"

Tentacles are also just ingrained in our psyche, like on old sea maps. Quite frequently, there's just, like, a tentacle coming out. There's always been this illusion insinuating that there's more going on, and I like to do that as much as possible. It really gets people to use their imaginations and fill in the blanks.

How were the tentacles made for this piece?

We used nylon, like hot-air-balloon type material. It's airproof, lightweight and strong. You also get some great colors.

We use little fans to keep them inflated. Over the time they've been here, Group X technicians have been keeping control of them. They've been changed a bit, to keep them fresh-looking. This was our Philadelphia experiment.

What are the challenges?

You can't make anything with flat sides, and there are certain shapes you just can't make easily. You have to be able to construct it.

You need to be aware that we're working outside, on buildings and roofs, so rather than keep things standing up against the wind, we try to make things that move with the wind.

Once you've started the design process and making process, you don't know how it looks until you blow it up. So every inflating is exciting, because it's like you're giving birth to a new baby or creature.

The maker and his massive monster installation.
JESSICA GRIFFIN / Staff Photographer
The maker and his massive monster installation.

Your work is often very brightly colored and hard to ignore. What are you trying to convey?

When you're making public art, you want to try and engage as many people as possible. Humor is a really good way of doing that. You want to stand out. You want to disrupt the skyline with bright colors for a short time and make people look up from their phones.

If you make people smile, you're really winning. With street art, you want to make people look at their city in a new light and get excited, have a laugh or take a picture.

A really strong theme of ours is also this idea of the enormity of nature, like it has suddenly appeared in the city on some kind of revenge attack, whether we've got giant green shoots bursting through the pavement or trees with eyeballs looking down at you, or tentacles bursting from a building, ready to tear society apart. You can convey a lot with a bit of humor.

There's a lot of darkness in the world and we like to bring a bit of fun, but there's more to it than just that.

Say goodbye to the sea monster from 5 to 8 p.m. Friday at 13th Street and Flagship Avenue. Egan will be onsite for a meet and greet. 

Monster and creator are out of here after Friday’s event.
JESSICA GRIFFIN / Staff Photographer
Monster and creator are out of here after Friday’s event.