Warming bottles

[LouLouF90]

Hello,
I'm trying to warm some expressed breast milk in a MAM anti colic bottle. I'm just using the warm water method but I don't understand how you're supposed to submerge the bottle in the water without standing there holding it for 15 minutes? (As the bottle floats) Does anyone have any tips? It doesn't seem practical to have to stand there holding it the whole time. Do all baby bottle float?

A stubby jug with a plate on the top to hold the bottle down?

Please don’t put that type of bottle into water. The unsterilised water goes into baby’s milk from the bottom. There is a tiny warning about it on the instructions, it was a thing a few years ago as some baby’s were getting ill from it. I used to use a cheap baby bottle to warm then pour into the MAM bottle x