My wife and I always use Reimann P20. When on holiday we always have the bottle in our bag just in case we need to reapply. This very rarely happens. We swim in the sea and the pool and dress for lunch and still do not have to reapply the protection very often. Neither of us have ever been sunburned since using P20. We have recommended P20 to numerous people and only one person has said they burned when using it. They only burned though because they applied the spray and instead of following the instructions, they then jumped straight into the water. This is the only sun protection that we use and cannot recommend it enough.