Tec divers spend a long time decompressing at various depths. Usually much longer than the actual dive length. Most of that time is spent in fairly shallow depths, just hanging on the anchor line.
I had an idea a while back to put an eBook reader like the kindle or nook into a ziplock bag and tie it to the line at 20 feet. Then, when you're spending 30+ minutes hanging out, pass the time with a nice book.
Now, DryCase is selling a watertight bag for your eBook reader or tablet that could serve a similar purpose. My idea would only work with an eReader, or something with physical buttons. This case works with products like iPad, with full touchscreen capabilities1. I'm doubting you'll get a good WiFi connection, though. :)
I guess the question is just if you're willing to take a $600 electronic underwater and tie it to a line in the middle of the ocean. I'd be curious if there are any tec divers out there. What do you do to keep yourself occupied?
1. The seller doesn't say the bag is approved for underwater use, or how deep you can take it.