Scorpions are immune to their own venom, thus this scorpion would be able to complete its task of ferrying the smaller scorpion across without succumbing to poison and dying.
Scorpions are not good swimmers, but they are proficient enough to survive for approximately 48 hours in water by breathing through their exoskeletons.
And a scorpion with 10 years industry experience in Frog will probably do a lot better than 48 hours