You can find Deinosuchus primarily in the swamp biome. Here’s the best way to tame one:

1. Find a high level one

2. Pick a spot near them use as your taming grounds

3. Clear out the trees and all creatures (they will distract the deino between feedings)

4. Grab the deino’s aggro with your flyer and lead it to the cleared space, then fly straight up

5. Collect prime meat from nearby animals (they spoil faster in your inventory than your flyer’s

6. Wait for the deino to stop, sit down, and open its mouth with a hissing sound

7. Then land your flyer (leave it in passive mode), approach the deino’s mouth from the side and feed it the prime meat (do not touch it!)

8. Quickly run back to your flyer and go up the avoid being bitten

9. Repeat steps 5 - 8 until tamed

P.S. Accidentally attacking or aggroing the deino won’t lower taming efficiency