"ether"!
(this is not meant to be substantive criticism of your idea; I just think it's funny how much this sounds like the 19th century concept of ether that was abandoned)
«To justify giving mass to a would-be massless particle, scientists were forced to do something out of the ordinary. They assumed that vacuums (empty space) actually had energy, and that way, if a particle that we think of as massless were to enter it, the energy from the vacuum would be transferred into that particle, giving it mass.»
I personally think of the water as space, rather than spacetime. I think time is a byproduct of space-mass interactions. I could of course be very wrong!