Crimson Tidestallion

Before doing anything else, visit Mrrl at 39.2, 54.2 in Nazjatar to confirm the Crimson Tidestallion is in his inventory that day — the mount only appears for roughly 2 to 4 days per month, so do not begin the trading chain until you have verified it is currently available.

Go to Murloco in his cave at 46.3, 32.6 in Nazjatar — you may need to check in War Mode if he is not present — and fight the nearby mobs to get him to spawn, then purchase 1x Hungry Herald's Tentacle Taco from him to begin the chain.

Find Mrrglrlr in Nazjatar and purchase 714x Slimy Naga Eyeball, then trade all 714x Slimy Naga Eyeball to Grrmrlg to receive 238x Curious Murloc Horn.

Trade 168x Curious Murloc Horn to Flrgrrl for 28x Ghost Food, then also purchase 288x Unidentified Mass from Flrgrrl, and trade 32x Just Regular Butter to Mrrglrlr for 16x Smelly Pile of Gloop.

Go to Hurlgrl in Nazjatar and trade 288x Unidentified Mass for 48x Dirty Murloc Sock, which washes into 48x Clean Murloc Sock; also trade 70x Curious Murloc Horn for 14x Healthy Murloc Lunch, and purchase 128x Sweet Sea Vegetable from Hurlgrl.

Trade 48x Clean Murloc Sock to Grrmrlg for 16x Sea Giant Foot Dust, and trade 128x Sweet Sea Vegetable to Flrgrrl for 32x Just Regular Butter — note that all items in this chain last only 24 real-time hours, so complete all trades and the final purchase from Mrrl at 39.2, 54.2 within that window.