There was a promotion a few days ago that says "Just log in with your Microsoft account and play Minecraft any time from May 31st 12:00 AM UTC – June 3rd 6:59AM UTC and earn Deep Sea Mash-up Pack free! That’s all you have to do, we’ll handle the rest. You can earn one map per person, and your free map will be accessible approximately a week after in your account in the Minecraft Marketplace, on (or before) June 12, 2019." I played Minecraft on June 1st, but even though (at time of writing) it's June 16th, I never received the pack.