There are two "ways" you can tame it each having upsides and downsides.

1. Build a trap lure it in and shoot it.

2. Use a creature like the Deinosuchus who has rider Weaponry enabled and have the creature tank while you shoot it.

If you use the first method its quick and easy but Ou gotta wait like for a while till it's tames.

If you use the second one it's alot more frustrating but on the flip side the Xiphactinus tames almost instantly once it's out. The reason for that is, if you shoot it with tranqs it will take damage, that will cause it to use its shredding move (that produces the red cloud) more often and it uses that cloud to rapidly heal itself. that heal will quickly drain its food so it takes very quickly