Algorithm 3 T-MM underwater acoustic-based location algorithm.

Input: Set the initial point ${\mathit{x}}_0$ by Algorithm 2 and the parameter $\eta$. And calculate distance $d_i$ by Equation (7) mentioned in Section 4. Output: ${\mathit{x}}_{\mathit{t}}$ Steps: 1: Set the number of iterations ${\mathit{t}}_{max}$; 2: Set $\mathit{t}=\mathbf{0}$; 3: if $t\le t_{max}$; 4:  if $\Vert \nabla f\left({\mathit{x}}_t\right)\Vert \le \eta$ 5:   Go to step 9; 6:  else if 7:   update ${\mathit{x}}_t$ as (24); 8:   $t=t+1$; 9: end if