The Underwater Arduino Data Loggers are working the Cave Pearl Project to develop a submersible data logger system for long-term environmental monitoring projects.

Here they discuss getting life & performance from CR2032 coin-cell batteries (3 volt):

“… you’ll discover that OEM test conditions are often proscribed to the point of being functionally irrelevant in real world applications. The simple question: “How much operating lifespan can you expect from a coin cell?” is difficult to answer because the capacity of lithium manganese dioxide button cells is nominalat best and wholly dependent on the characteristics of the load.”

“CR2032’s only deliver 220mAh when the load is small: Maxell’s datasheet shows that a 300 ohm load, for a fraction of a second every 5 seconds, will drop the capacity by 25%. But if the load falls below 3μA then the battery develops high internal resistance, reducing the capacity by more than 70%.

Surprisingly little is known about how a CR2032 discharges in applications where low μA level sleep currents are combined with frequent pulse-loads in the mA range; yet that’s exactly what a datalogger does.

See their analysis here.