If you live or work on Yokosuka Naval Base, you most likely look out over Tokyo Bay at some point during your day. Have you ever peered down into that green, murky water and thought about what lies below the surface?

If you are picturing a lot of muck and silt, then you are not very far off. You would probably assume there isn’t much to see in that type of environment, but the opposite is true. Those murky green waters are teeming with life, and when you dive below the surface you never know what you will discover.

While there are many fantastic diving spots around the Miura peninsula and beyond, there are two spots on base where you might see divers in the water: Green Bay Marina and Recreation Bay. Both are full of weird and wonderful sea creatures. Upon descending below the surface, you’ll likely encounter moon jellies slowly pulsing along in the water column. These translucent beauties are harmless to humans, with the worst-case scenario causing some irritation to your skin. The ones you must look out for are the sea nettles with their long, trailing tentacles that can be very painful if you come in contact with them.

Once you reach the mucky, silty bottom at around 15 to 30 feet, you’ll come across large sea hares, sea cucumbers, and massive solitary sea anemones just swaying in the current catching tiny phytoplankton with their long white and purple tentacles. My absolute favorite creatures to find underwater are nudibranchs and lucky for me Green Bay and Recreation Bay has them in abundance. Nudibranchs are essentially very pretty slugs that can breathe underwater.

They are an incredibly diverse group with over 3,000 species varying in color, size and shape. Some are so tiny you can barely see them whereas others are the size of a football. Nudibranchs can be identified by their rhinophores which look like little bunny ears popping out of the top of their head. Since they have terrible eyesight, they use these to sense chemicals dissolved in the water allowing them to find food. They also have feathery like external gills near their backside allowing them to breathe.

More fun finds in the muck include squid eggs half buried in the sand, flatworms and sea stars slowly cruising along the bottom in search of food, and lots of baby fish trying to hide in any algae they can find. If you’re looking for something other than just the little critters I’ve also run into a couple sharks, cuttlefish, and rays. The rays usually tend to see me first and all I get left with is a massive cloud of silt in the face. Every time I’m underwater it feels like a treasure hunt. Sure, the visibility is usually pretty low, and it gets pretty darn cold in the winter months but I’m happiest when I’m off looking for critters under the water.

If you’re a certified diver there’s a wonderful club on base called the Yokosuka Bubble Club, and for a reasonable yearly membership fee, you have access to all the tanks and dive buddies you could want. There is usually someone diving most weekends at Hayama and they also have plenty of day and weekend trips to dive sites along the Izu peninsula, Jogashima, and along the coast of Chiba prefecture. If you’re not certified and looking to get underwater, MWR offers basic open water SCUBA classes and rental gear.