Does the briefcase open?
No, it does not. We need to seal the case shut for best sound performance. We experimented with having it open, but in the end it wasn't worth it. Apologies.

Can I play guitar on it?
Any instrument you wish, really. The second audio channel (1/4"-inch) can play along with the Bluetooth channel, with it's own volume control. (Yes, Karaoke)

Can I charge the BASSMAKER using my car?
With a simple inverter of less than 100 watts you can plug in your charger and charge your BASSMAKER in the car.

How does it do in water?
It is fairly water resistant. The speakers are designed for the elements, as is the case and the material covering it. However, the case cannot be submerged in water. Keep it on the dock. If for whatever reason the case ends up in the water, get it out and dry it off for 72 hours before turning it back on. Do not leave the outside of the case wet; pat dry.