A private canal?

On our way to Fenny Compton Wharf, in about the Priors Hardwick area, we came across a boat seemingly on dry land.

As we got nearer we could see that it was actually sitting in its own little pool of water, not much bigger than the boat itself.

There is no connection to the canal, not now, anyway. The boat is obviously inhabited. Why all the effort to dig out the pool rather than moor at the edge of the field? I suppose it saves having to pay CRT for the mooring. Another question I asked myself is, as it can't go anywhere, why not simply sit it on dry land? One reason might be that you need water to cool the skin tank if the engine is run (to charge batteries, say). Although the limited volume of water wouldn't be able to carry away the waste heat as efficiently as the comparatively infinite amount of water in the canal.