Pump for an ROV

Some while back, ferrofluids encapsulated behind a flexible sheet rubber(silicone?) membrane were considered for marine propulsion. The undulations of the 'bag' of ferrofluid activated in sequence, think 'centipede' think 'electromagnet & Iron fileings' like a flat-fish, initiated propulsion. You stipulate some sort of 'blocking' mechanism? Perhaps you might investigate some kind of 'peristaltic' electro-fero-fluid pump, to coin a pun, If your 'heart' is set on this ROV project, work rest and play at it.

Sounds like a novel form of peristaltic pump. Kinda neat.

Ferrofluids can theoretically be used for many types of pumps but the amount of power produced is limited by low magnetic saturation and permeability. Magnetic forces are typically two orders of magnitude lower than that of steel or ferrite. For locomotion or high mass flow applications, ferrofluids don't offer any value. They do have some niche value in biomedical fields though.

My first reaction is use a bilge pump - obtainable at the local ships chandlers (or on-line)

The 'need to knows' here are;

1. the head, or height of lift required, as this controls volume

2. the water quality variance between 'into' and 'out of'.

I.e. It would not be appropriate to use the same pump if one is supply and the other waste.

I'm assuming "ROV" is a land vehicle - not a ROV. But if the latter, I can suggest pumps suitable for ballast trimming.