The definition of “coastal waters” is contained in 33 C.F.R. § 175.105(b). “Coastal
waters” includes the waters of the Great Lakes, the territorial seas of the United States,
and:
Those waters directly connected to the Great Lakes and territorial seas (i.e., bays,
sounds, harbors, rivers, inlets, etc.) where any entrance exceeds 2 nautical miles
between opposite shorelines to the first point where the largest distance between
shorelines narrows to 2 miles, as shown on the current edition of the appropriate
National Ocean Service chart used for navigation. Shorelines of islands or points
of land present within a waterway are considered when determining the distance
between opposite shorelines.
As you are planning on paddling the Chesapeake Bay and possibly the barrier Islands, if paddling after sunset you would need, in addition to least a flashlight or other white light that can be shown to avoid a collision, some sort of nighttime emergency distress signal, as most of the Chesapeake Bay qualifies as coastal waters.
For a light, any dive shop carries suitable waterproof flashlights and many can be found online. Some people use a waterproof headlamp, but these have the disadvantage of blinding others when you turn to look at them. Some people use a pedestal type LED light on their back deck. Do not use a strobe. That’s an inland waters distress signal and can be confused with a navigational marker. Navigation lights can be used but are not required on a kayak. I also have a light the fits on the strap of my PFD in case of the unlikely event that I became separated from my boat.
While the light does not have to be on, I always have mine on after my wife and I were nearly run down by a dingy with an electric motor running illegally with no lights, when we had our lights off to enjoy the stars.
There are many types of nighttime USCG approved distress signal, such as starting a fire on your deck, but the most practical for kayaks are three areal flares. They can be hand launched or pistol launched, typically made by Orion. In one of our classes we received the appropriate permissions to demonstrate these flares. Fully 85% of the hand launched flares failed after being carried on a boat for a season, in spite of being in the original packages and stored in drybags. After seeing this I went with the 25mm pistol launched flares. In subsequent demonstrations I’ve never had one fail, even a flare 10 years old. Flares have an expiration date and must be periodically replaced.
Within the last few years Orion has come out with an electronic USCG approved nighttime distress signal. but it is bulky, expensive, and a bit too large for most kayaks.
Nighttime distress signal must be USCG approved, in date and serviceable, and readily accessible. I carry the flare pistol in a tethered drybag behind my seat with other emergency gear. Ideally, it would be good to have it on my PFD, but it is too bulky with the other gear I’m carrying. It is questionable whether carrying flares in a sealed hatch that can’t be accessed from the cockpit would qualify as readily accessible. Be wary of manufacturers that claim that their lights are USCG approved. They may be approved for other purposes, but almost none are approved as a nighttime distress signal. Requirements for these are very onerous.