This paper presents an inverted ultra-short baseline (iUSBL) simultaneous localization and mapping (SLAM) based on Unscented Kalman filter (UKF) with current compensation. The complexity of the underwater environment prevents the use of Global Positioning System (GPS) or visible-light cameras, thereby we rely on an acoustic positioning system to achieve autonomous underwater vehicle (AUV) navigation relative to the beacons. Our system considers using an AUV equipped with a time-synchronized iUSBL array to measure the range and angle between vehicle and acoustic beacons via one-way travel-time. Then, we propose UKF-based online SLAM to filter these acoustic measurements, meanwhile, add current compensation which is inherent underwater. In contrast, traditional SLAM applications usually contain a large number of landmarks, this iUSBL acoustic system only needs sparse beacons to estimate the vehicle pose. Consequently, it does not cause UKF to have an excessive computational burden. The validity of the proposed method is confirmed by numerical results. In particular, the proposed algorithm prevents cumulative errors from growing quickly quite well when using double beacons.INDEX TERMS Acoustic localization, inverted ultra-short Baseline, unscented Kalman filter, simultaneous localization and mapping, sea currents estimation.