I also have a PoolBlaster Max. It does an amazingly good job and can work about as fast as a vacuum head connected to your main pump/filter. The battery life is amazing and I've had mine for maybe four years and the rechargeable batteries still hold a good charge.
However, I think all pool vacuums are designed to operate fully submerged and even the smallest ones that use disposable batteries need 2-1/2 or more inches of water. The PoolBlaster Max needs at least about 8" of water if you're careful to use it angled downward. That said, the PoolBlaster Max has a round tube at the suction end that mates with attachments, similar to a household vacuum wand. I suspect a short piece of flexible tubing could be used to connect some sort of vacuum head to the PoolBlaster and allow the head to vacuum in very shallow water while holding the vacuum barely below the waterline. Maybe worth trying but they don't give these things away. My daughter bought a regular PoolBlaster (not the MAX version) and I wasn't impressed with that version and wouldn't recommend it.