A boat carrying a large number of stones is floating in a water tank, if the stones are unloaded into the water in the tank, the level of water

(if stones sinks) they can displace water equal to V_S . i.e.

Volume of stones ${\text{V}}_S\text{=}\frac{{\text{m}}_{\text{s}}}{{\text{d}}_{\text{s}}}\to \left(\text{1}\right)$

Volume of water displaced by stones together initially (before dropping) ${\text{V}}_{\text{D}}\text{=}\frac{{\text{m}}_{\text{s}}}{{\text{d}}_{\text{w}}}\to \left(\text{2}\right)$

Being present in boat floating

They can avail upthrust V_D × d_W = m_S

From (1) & (2)

${\text{V}}_{\text{D}}>{\text{V}}_S$                              $\because {\text{d}}_{\text{S}}>{\text{d}}_{\text{W}}$

If the stones are unloded  into the water in the tank,  so they can displace V_S < V_D the                                                                                                                      level of waterfalls.