Shade
Monster Junkie
Good point about aquatic trippoing...try this one from Oriental Adventures instead:
Unbalancing Strike [General]
You can strike a humanoid opponent's joints to knock your target off-balance.
Prerequisite: Improved Unarmed Strike, Stunning Fist or monk's stunning attack, Wis 15+.
Benefit: Against a humanoid opponent, you can make an unarmed attack that has a chance of unbalancing your target. If your attack is successful, you deal normal damage and your target must attempt a Reflex saving throw (DC 10 + 1/2 your level + your Wisdom modifier). If the target fails this saving throw, he is thrown off balance for 1 round, losing any Dexterity bonus to AC and giving attackers a +2 bonus on their attack rolls.
But you're probably right that IBR is enough.
Unbalancing Strike [General]
You can strike a humanoid opponent's joints to knock your target off-balance.
Prerequisite: Improved Unarmed Strike, Stunning Fist or monk's stunning attack, Wis 15+.
Benefit: Against a humanoid opponent, you can make an unarmed attack that has a chance of unbalancing your target. If your attack is successful, you deal normal damage and your target must attempt a Reflex saving throw (DC 10 + 1/2 your level + your Wisdom modifier). If the target fails this saving throw, he is thrown off balance for 1 round, losing any Dexterity bonus to AC and giving attackers a +2 bonus on their attack rolls.
But you're probably right that IBR is enough.