It is not an "additional" battery, it is the lithium Ion battery is included by the manufacturer. You'll get the camera/housing, battery and cable as indicated.
By boyfriends is a scuba diver. I want to get him the GoPro Silver. What other accessory does he absolutely need to dive with it?
Bob (Certified Scuba Instructor at Scuba.com)
The camera will work, as is. To make it more equal to other underwater cameras you need to add the LCD Touch BacPac, and the Red Filter. It is also not ready for use with an external light source. To use a normal tray and arm assembly, you'll need the Gopro Tripod Mount. Also, keep in mind the Gopro was primarily designed for video. To capture stills the user will have to learn how to manipulate them with software on their computer.
Not only is the HERO3+ Silver Edition 15% smaller and lighter than previous models, it’s 2x more powerful—making it the most advanced Silver Edition camera yet. Wearable, gear-mountable and waterproof to 131’/40m, it captures professional-quality video at resolutions up to 1080p60 and 10MP photos at up to 10 frames per second. With faster built-in Wi-Fi, enhanced low-light performance and 30% longer battery life, the HERO3+ Silver Edition makes capturing and sharing your life easier than ever.
Advanced Video Capture Settings Spot Meter: Ideal for filming within a dark space with the camera pointed towards a brighter setting (such as filming the outdoors from within a car).
One Button: Upon powering on, the camera automatically begins recording video or capturing Time Lapse photos.
Looping Video: Records a continuous video loop that overwrites itself until you press the shutter button to stop it. It's ideal for saving space on your memory card while waiting to catch a moment of action.
Photo Modes Overview Photo: Capture a single photo.
Burst Photo: Capture up to 10 photos per second - perfect for fast action photography.
Time Lapse: Automatically capture a series of photos at timed intervals. Ideal for capturing photos when the camera is out of reach.
Image Quality Optics
Improved image sharpness and low-light performance compared to HERO3: Silver Edition
Ultra-sharp 6-element aspherical glass lens
Fixed f/2.8 aperture
Ultra wide angle field of view
Mono, 48kHz, AAC compression with AGC (automatic gain control)
Increased audio range by approx. 10dB compared to HERO3: Silver Edition
Handles approx. 2x greater volume without distortion compared to HERO3: Silver Edition