Opportunistic feeders, their diet varies from one region to another. In the Antarctic, killer whales eat about 67% fishes, 27% marine mammals, and 6% squids. Killer whales in the Bering Sea (near Alaska) eat about 65% fishes, 20% squids, and 15% marine mammals.
Even though your shower grout looks dry, using it too early or sealing it before it's ready may damage it, leading to premature failure. Most cement-based grouts require a cure time of 48 to 72 hours before applying a penetrating sealer.
All you need to do is leave the grout to dry before getting it wet. The instructions should tell you for how long. As you and others have pointed out drying and curing are separate things. While you can use the shower after the grout is dried you may need to leave it for a day or two after it's cured before sealing.