This spell functions as sea steed, but as long as you stay mounted on the target, you also gain the amphibious quality and your melee attacks function as if you were under the effect of freedom of movement. the benefits you gain from this spell are not polymorph effects. If you dismount from the target, you retain the amphibious quality for up to 1 minute, but not the other benefits. You regain all of the benefits once you mount the target creature again.
Pathfinder Roleplaying Game Ultimate Wilderness © 2017, Paizo Inc.; Authors: Alexander Augunas, John Bennett, Robert Brookes, John Compton, Dan Dillon, Steven T. Helt, Thurston Hillman, Eric Hindley, Mikko Kallio, Jason Keeley, Isabelle Lee, Jason Nelson, Stephen Radney-MacFarland, Alex Riggs, David N. Ross, David Schwartz, Mark Seifter, Jeffery Swank, and Linda Zayas-Palmer.