When cooking lobster tails in boiling water, timing is crucial to achieve the perfect texture and flavour. A general rule of thumb is to cook the tails for about 1.5 to 2 minutes per ounce. For example, a 6-ounce lobster tail should ideally simmer for approximately 9 to 12 minutes. Ensure that the water is at a rolling boil before adding the tails, as this helps to cook them evenly and thoroughly.