What's the adjective for submergence? Here's the word you're looking for.
Included below are past participle and present participle forms for the
verbs submerge and submerse which may be used as adjectives within certain contexts.
“Be sure to include submergent plants such as common waterweed and hornwort for their high oxygen output.”
“Most plant dry mass in the diet of Barrow's Goldeneyes consisted of seeds of submergent and emergent macrophytes, particularly those of pondweeds, mare's tails, and bulrushes.”
“They prefer clear water in small lakes and ponds that are not overwhelmed with submergent and emergent vegetation and which do not support populations of fish.”
submerse
Denoting or characteristic of a plant growing entirely under water.