Even more convenient but still waterproof and durable
When you're ready to charge, simply unscrew the waterproof cap, pull out the battery capsule, and plug it into a micro-USB cable and your power supply of choice or computer.
Charge time is about 3-5 hours.
AAs to stay
We're still making the M204, M210 and M232 with the standard AA batteries if that's what you prefer. Sometimes having the option of AA batteries is more convenient because they're easier to buy at a local store if you're out and about, or because you already have a number of AA batteries at home.