Try and reduce your time spent in the shower by one minute.
Collect rainwater in buckets or a water butt to use on your garden or put a bucket in the shower while you are washing to give the water a second use.
Using the dishwasher for a full load is better than washing by hand. Use eco mode.
Instead of using huge volumes of water to fill a paddling pool in the summer months, maybe you could have a dip in a local river, lake, the sea or an outside pool.