Hold Breath. The tanystropheus can hold its breath for 20 minutes.
Bite. Melee Weapon Attack: +4 to hit, reach 10 ft., one target. Hit: 6 (1d4 + 2) piercing damage. If the target is a tiny creature, it is grappled (escape DC 11), and the Tanystropheus can't bite another target. While a creature is grappled this way, it is also restrained.