This bug has long, fuzzy legs that support it on the water's surface as if the creature stands on solid ground.
Giant Water Strider CR 1
XP 400
N Large vermin
Init +1; Senses darkvision 60 ft., tremorsense 60 ft.; Perception +4
Defense
AC 12, touch 10, flat-footed 11 (+1 Dex, +2 natural, –1 size)
hp 19 (3d8+6)
Fort +5, Ref +2, Will +1
Immune mind-affecting effects
Offense
Speed 30 ft., fly 20 ft. (poor)
Melee 2 claws +2 (1d4+1), bite +2 (1d2+1)
Space 10 ft.; Reach 5 ft.
Statistics
Str 13, Dex 13, Con 14, Int —, Wis 10, Cha 2
Base Atk +2; CMB +4; CMD 16 (24 vs. trip)
Skills Fly –5, Perception +4, Swim +5; Racial Modifiers +4 Perception, +4 Swim
SQ water skating
Ecology
Environment any water
Organization solitary or colony (2–9)
Treasure incidental
Special Abilities
Tremorsense (Ex) A water strider's tremorsense functions only when the creature is in contact with the water's surface.
Water Skating (Ex) A water strider can move on the surface of water as if it were on land. A water strider swimming at the water's surface can pull itself onto the water with a successful Swim check.
A giant water strider is a long-legged insect with the ability to walk on water. It feeds on fish and birds. Water striders use their weak flight only to escape predators or for seasonal migrations to new breeding areas. They are sometimes kept as mounts by coast-dwelling humanoids. A giant water strider lives 1–2 years.
Carrying more than a light load (200 pounds) prevents a giant water strider from using its water skating ability.
These small, immature water insects are easily supported by the water's surface tension.
Nymph Water Strider CR 1/4
XP 100
N Small vermin
Init +2; Senses darkvision 60 ft., tremorsense 60 ft. (see giant water strider); Perception +4
Defense
AC 13, touch 13, flat-footed 11 (+2 Dex, +1 size)
hp 4 (1d8)
Fort +2, Ref +2, Will +0
Immune mind-affecting effects
Offense
Speed 30 ft., fly 20 ft. (poor)
Melee 2 claw –1 (1d3–2), bite –1 (1d2–2)
Statistics
Str 7, Dex 15, Con 10, Int —, Wis 10, Cha 2
Base Atk +0; CMB –3; CMD 9 (17 vs. trip)
Skills Fly +0, Perception +4, Swim +2; Racial Modifiers +4 Perception, +4 Swim
SQ water skating (see giant water strider)
Ecology
Environment any water
Organization solitary or colony (2–9)
Treasure incidental
A nymph water strider is an immature specimen of the giant water strider—more mature than a caterpillar but not yet an adult. Over the next several months it eats and molts, increasing in size with each molt until it becomes Large and is fully adult. These creatures are shy and more skittish than adults.
Lizardfolk hunt wild nymph water striders, and consider them a wonderful delicacy. Boggards and gripplis raise them as food animals, but something about the domestication process makes such nymphs unappealing to lizardfolk. In the wild they frantically flee other creatures that approach them, making them difficult to hunt or corral. Many boggard, lizardfolk, and grippli tribes consider capturing a live nymph a rite of passage to adulthood.
A nymph water strider isn't suitable as a mount for any Large or smaller creature.