When your favorite training pool is closed and you have a home pool with limited space, why not try this out? Using an old mountain bike tyre tube around my waist, I have attached a bungee cord to it and suspended the cord from a solid object on land.
Focusing on balance, strength and technique of one arm pulling at a time. With the bungee cord giving a fair amount of resistance this exercise will strengthen those arms. A strong kick is required so add flippers if you are a weaker swimmer or struggling to stay afloat on this one.