In one general aspect, various embodiments are directed to ultrasonic surgical instruments that may be used in aqueous environments. The instruments may include cutting a member that is supported within a hollow sheath. Various seal arrangements are disclosed for establishing a substantially fluid-tight seal between the cutting member and the sheath.1つの一般的な態様において、様々な実施形態が、水性環境で使用され得る、超音波外科用器具を対象とする。器具は、中空のシース内に支持される部材の切断を含み得る。