This letter addresses the problem of interval velocity estimation for unmanned underwater vehicles subject to multiple model uncertainties. We extend our previous works to the case of large initial bounds on uncertainties by introducing an adaptive mechanism. For improving the accuracy of interval estimation, $H_{\infty }$ approach is used in the design of interval observer to attenuate the effect of uncertainties. Sufficient design conditions are formulated as a set of linear matrix inequalities. Simulation results demonstrate the effectiveness of the proposed method.