U can also spay with water as the jet from a spray bottle will blast them from foliage. If u want to submerge them in something. Submerge ur plant in a neem or neem based mix (mix according to instructions. Actually mix a little lighter than instructed. Dipping is easier than spraying.Just be aware that the weight of the liquid will cause ur plant to lean and can cause the stem to bend branches to break and roots to tear. After dipping (while supporting the lower stem), gently shake the plant to remove excess liquid form weighing the plant down. Add support for the young wet plants. What ur asking is the equivalent of a person with crabs, lice, or scabies thinking they can drown them in a tub or pool. It won't happen. Good luck.
If u can see them, U can smash them. U can use ur thumb and forefinger. Just be sure not to touch unaffected plants or too much of anything until u wash ur hands. Don't wanna transfer eggs or hitchhikers anywhere but the sink. U'll know how many u've smashed by the # of yellow/orange streaks/spots on ur thumb. Manual removal is effective to help control populations, every little bit helps.For those that don't know what they're looking at, this is the underside of a leaf. The black spots are the spider mites. Nice ,clear pics!