My goals for the project are:

1. The hardware must fit inside my seashell
2. The device must include a rechargeable battery
3. The device must have an on/off switch
4. The device must have a radio for streaming content
5. The device must have a speaker for sound output
6. The device may need to process the streaming content, to convert it into suitable output
7. I will need to find a suitable source of live ocean sounds

The most obvious solution to the hardware goals would be to repurpose a small bluetooth radio. The bluetooth radio could be taken out of its case and placed inside the seashell. The bluetooth radio could then be paired with another device that would select and decode the content stream, leaving the hardware side of the project done. At the moment, I don't like this approach for a couple reasons. First, I would need a second device to pair with the seashell, which would have to stay near the shell. Second, that approach seems less magical (more magical is a non-functional project requirement) than making the shell entirely self-contained. The Bluetooth speaker option would still meet the project goals though, so I will keep it as a backup option.

My preferred choice of hardware is an ESP8266. The ESP8266 can theoretically handle connecting to a WiFi router, opening an mp3 stream, decoding the stream, and driving a small speaker. This project ( https://github.com/espressif/esp8266_mp3_decoder ) describes an mp3 decoder running on the ESP8266. The Hackaday article about the web radio shows the ESP8266 offloading the decoding and speaker driving to a VS1053 chip ( https://hackaday.io/project/11570-wifi-webradio-with-esp8266-and-vs1053 ).

For the source of the ocean sounds, a good candidate seems to be the Salish Sea hydrophone network ( http://www.orcasound.net/ ) which consists of several hydrophones in North-west Washington. Listeners report hearing Orcas during their migration, but otherwise there is a soothing ocean noise. VLC reports that the stream is "MPEG layer 1/2 (mpga)". OrcaSounds notes that this is a ShoutCast stream. Unfortunately, I don't know how compatible these codecs are, or how easy it will be to decode them.