summersus
Could not find submersum in Logeion dictionaries.
submersum Noun: masculine accusative singular of summersus
summersus (subm-), a, um, Part. of summergo.
summersus (subm-), ūs, m. [summergo],
- a plunging under water, sinking (post-class.), Tert. Anim. 32 med.