Final answer:
According to the 'Iceberg effect' in Biology, a. stability and c. endurance are considered foundational adaptations for aquatic life to survive under the water during winters.
Step-by-step explanation:
According to the 'Iceberg effect' in Biology, the adaptation of an organism to survive under the water involves multiple factors. One of the foundational adaptations is a. stability.
When ice forms on the water surface during winters, it acts as an insulating layer for aquatic life underneath, providing stability for their survival. Additionally, c. endurance is also an important adaptation as aquatic life needs to withstand the harsh conditions of low temperatures and limited resources during winter.