If you've been shooting this thing with tranq arrow and then you need to go back to your base for something before you knocked out it, give up. This thing torpor drain rate is extremely high, missed shot is already a big mistake. You'll end up killing the mosa instead of knocking it out. Sarco is highly recomended for water mount, bringing army such as basilo is a stupid idea, mosa is the strongest water creature, your basilo won't survive. Use the pokeball thing to bring your basilo, i know mosas territory is so damn dangerous not because of the mosas, but the electric eels and jellyfish, also if your sarco has 500% damage or more, you could kill plesio and alpha shark without killing your mount, atleast in one vs one battle, not one vs herd.

Up the arrow right now, this is a critical information for beginners.