I’m passing on some information here as shared by my friend and fellow sailor Wolfgang who has experience sailing and motoring in Tokyo Bay. Tokyo Bay has some unique navigational rules. Because it is such a busy shipping port there is a massive amount of freighter traffic going in and out at all times. The shallowness of the bay means that all these ships must pass through a very narrow stretch of water off of Kisarazu. The normal rules of the road don’t apply, and pleasure boats are forbidden from traveling in this area. Pleasure boats can cut across at right angles, but must clear the area as quickly as possible. Here’s a map showing the designated shipping route in the center of the bay:
Just off of Kisarazu there is a small island. Pleasure boats traveling on the Chiba side of the bay need to pass to the east of this island in order to safely stay out of the shipping lanes. However, it’s very shallow here so it’s important to check the tide charts beforehand. Here’s a closeup of the area:
There’s also a restricted area around Haneda airport marked by yellow buoys. If one approaches too close to this area the harbour patrol will chase you away. I made the mistake of getting too close in a rented motorboat one time, and the harbour patrol not only chased us out of the area, they continued to follow us for quite a distance. My understanding is that this area is kept free of marine traffic in the event that an aircraft had to make an emergency water landing, and perhaps they also want to keep it clear out of security (terrorism) concerns. I suppose two foreigners in a motorboat zigzagging about seemed quite suspicious to the harbour patrol!