Amphibious. The frog can breathe air and water.

Bellowing Croak.  The frog utters a loud croak capable of momentarily stunning prey.  All creatures within 20 feet of it that can hear it must succeed on a DC 11 Constitution saving throw or be stunned for 1 minute.  Creatures immune to thunder damage automatically succeed on their saving throw.  A stunned creature can repeat the saving throw at the start of each of its turns, ending the effect on itself on a success.

Standing Leap.  The frog's long jump is up to 20 feet and its high jump is up to 10 feet, with or without a running start.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (1d10 + 2) piercing damage, and the target is grappled (escape DC 12).  Until this grapple ends, the target is restrained and the frog cannot bite another target.

Swallow. The frog makes one bite attack against a Medium or smaller target it is grappling.  If the attack hits, the target is swallowed, and the grapple ends.  The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside the frog, and takes 7 (2d6) acid damage at the start of each of the frog's turns.  The frog can have only one target swallowed at a time.

If the frog dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, exiting prone.