The order is huge and has many varieties that specialise, but this is what a typical wasp as far as most people are concerned looks like....
but this is a honey bee..
Without positive identification from you to go on I'm not sure what the ones you are seeing might be but honey bees do collect water for the hive and I have seen small groups of them, say about 8 or so, go to moist soil, or even places where the dog has pissed on our gravel path.
Worker bees during their lives tend go through quite specific phases of jobs, one of which will be collecting water, so quite possibly these water carriers may be turning up mob handed if one of them locates a source such as your recently overturned soil.
As for the bee hotel idea, I wouldn't worry too much about honey bee swarms as these hotel things are just not designed for honey bees, the internal dimensions are all wrong and honey bees tend to be very picky over such details so it's highly unlikely you would get a swarm attracted to one.
The hotels are largely designed for the different types of bumble bees of which there are many. See here...
http://bumblebeeconservation.org/All these different types tend to specialise in different flowers/crops, bumbles generally have much longer tongues than honey bees so actually contribute a bit more to pollination diversity.
But I will say these hotels are well worth it for conservation and ensuring variety.