IPA: /səbˈmɜːrdʒəbl/
KK: /səbˈmɜrʤəbl/
Able to be put underwater or to stay underwater without being damaged.
The engineers designed a submergible vehicle to explore the ocean depths.
Submergible is formed from "sub-" (meaning under) and "mergere" (meaning to plunge or immerse). The word describes something that can be plunged or immersed under water.
Think of something that can go 'under' ('sub-') the water by 'plunging' ('mergere') — that's what submergible means.