How does conservation of momentum work when at least one of the bodies in the problem changes mass?

The principle to use here is the principle of conservation of linear momentum, the question asks whether we have to modify this principle or use it in a different way to solve physics problems that have a body that changes mass over time. The answer is that conservation of momentum works in every situation apart from when an external force acts on a system. So, the only other thing we need to solve one of these types of problems is care in each step and when applying the principle of conservation of momentum.To illustrate this, I have a physics problem with bodies of changing mass, namely squids!Question: Squids use jet propulsion to move by rapidly ejecting water from a cavity. If a squid weighing 7kg (including the mass of water in the cavity) that is initially at rest then spots a predator and rapidly ejects 1.5kg of water to give itself an escape speed of 2.5 m/s, at what speed must the water be ejected? Ignore any drag effects of the surrounding water.Answer: We set up the known values with symbols.Mass of squid with water Msw = 7 kg, initial speed of squid Vinitial = 0 m/s, mass of squid without water Ms = 7 – 1.5 = 5.5 kg, mass of ejected water Mc = 1.5 kg, speed of escaping squid Vescape = 2.5 m/s and speed of ejected water Vwater = ?Conservation of linear momentum:Msw X Vinitial = Ms X Vescape – Mc X VwaterHence Vwater = 9.2 m/s to two significant figures.