Is the detecting head waterproof? Can I search under water?

Yes the coil is impermeable.
With regard to actual underwater detecting, this is only possible at very shallow depths, for example in a stream where the coil will only be immersed by a few centimetres. This is not due to any waterproofing problem, but rather because the wireless radio link cannot pass through a greater volume of water.
We will in the future be offering a special accessory, a passive waveguide (not powered) which will clip onto the coil and allow it to operate when immersed more deeply.
With regard to actual underwater detecting, this is only possible at very shallow depths, for example in a stream where the coil will only be immersed by a few centimetres. This is not due to any waterproofing problem, but rather because the wireless radio link cannot pass through a greater volume of water.
We will in the future be offering a special accessory, a passive waveguide (not powered) which will clip onto the coil and allow it to operate when immersed more deeply.