Hydrostatic pressure - weight of water above any point in lake, river or ocean. Water is heavy - every 10m in depth increases the pressure by 1 atmosphere. No evidence that any microbes are affected by pressure differences from sea level up to mountain tops or from sea level down several thousand meters in ocean. Water availability - not problem in aquatic environments. Is problem in terrestrial environments.
Microbes avoid problem by becoming inactive.
Odd habitat for desiccation and radiation protection - inside rocks. Cryptendolithic - actually live in rock matrix, several mm below surface. Hot deserts are so stressful that endoliths are limited mostly to cyanobacteria - Chroococcidiopsis.