In the framework of the PRIN PNRR 2022M7S2J SeaForSoil project, the exploitation of biopolymers from marine extremophiles, which play an important role in situ for survival in adverse environmental conditions including dehydration, could contribute to the development of new strategies to increase soil water retention in water scarcity conditions. To investigate the hydrating capabilities of biopolymers (BSs) produced by thermophilic bacteria, Bacillus licheniformis B3-15, B. horneckiae SBP3 and Bacillus sp. s7s-3ng, isolated from shallow hydrothermal vents of the Eolian Islands, in this study we evaluated the following characteristics: i) wetting properties, by measuring the reduction of the water contact angle on a polystyrene surface, ii) structural changes at increasing hydrating states (from 0 to 160% w/w of water content), using ATR-FTIR spectroscopy, and iii) water uptake from air at 90% of relative humidity, and the water-releasing rate under desert-like solar intensity conditions (>1300 W/cm²), using the gravimetric method. After growth under optimized conditions for 48h, the crude extract yield was the highest for BS B3-15 (1.5 g/L), followed by BS s7s-3ng (1.1 g/L) and BS SBP3 (0.950 g/L). Although all were chemically attributed to lipopeptides, each BS possessed different chemical structures and consequently different properties, with BS s7s-3ng being the most active in increasing the surface wettability (Ɵ =38), suggesting its use to easily spread wetting over a large area of solid surfaces. BS-s7s-3ng and BS SBP3 were more efficient in capturing liquid water (80%) than BS B3-15 (60%). BS SBP3 showed the highest water uptake from air (68%), and the slowest release of 90% of the up-taken water weight (within 13h) than BS s7s-3ng (7h) and BS B3-15 (4h), under exposure to high solar irradiation. As non-toxic wetting and moisturizing agents, these biopolymers could compete with industrially manufactured additives in agriculture to counteract soil dehydration.