Limosella vesiculosa continues flowering when the water level drops, leaving it high and somewhat dry but not in drought. The flowering season for this plant could not be determined. The photo was probably taken in summer and some other limosellas flower in spring or summer.
Some aquatic flowers are like frogs or other amphibians that live in as well as close to water. The plants increase much via vegetative reproduction from the trailing stems rooting at nodes, particularly when stems can spread across water surfaces. The roots and repeated rooting of L. vesiculosa serve in stabilising the banks of wetlands (Leistner, (Ed.), 2000; iNaturalist; https://www.botanicalrealm.com).