Can you heat the water?
This is a common question in the UK and the answer is yes, the water can be heated to 27 degrees C or in some special cases higher than that. (We recently completed a project which requires the swimming water to be at 30 degrees C all year round, but this required a very specific design.)
However we generally recommend that people try their pool first, for one season, without heating. We can always install the necessary pipework during the construction stage and if required, connect it to a heating system at a later date.
People very often ask about heating when we first talk to them, but we usually find that once they are swimming in the pond temperature is not the issue they thought it was beforehand. Particularly for natural designs, water in the shallow areas heats up quickly in the sun and can raise the natural temperature of the whole pond to 24 or 25 degrees C in summer periods.
Perhaps more importantly, natural water feels much more comfortable on the skin and is not as "harsh" as chemical water. So what might feel cold in chlorinated water, 22 degrees C for example, actually feels comfortable in natural water.
But the bottom line is yes - we can heat your swimming water, basically to whatever temperature you like.