What kind of horse can swim under water and never take air? Our Seahorse of course Usually we swim in pairs and we try to avoid becoming the next meal of our Crab. Their dorsal fins beat up to 35 times per second while swimming. have no teeth or stomach. Retail Package : 7.48" (W) x 1.77" (D) x 5.51" (H), Weight : 0.3 lb