I would turn off the breaker to that outlet and see if it repeats.
If it happens when the breaker is off then turn off the house main and see if it repeats.
Once its not repeating remove the cleaner from the pool.
How old is your pool?
The pool may not be bonded and that may be part of the problem. Bonding distributes the electrical potential so that you don't get shocked. If your pool is not properly bonded, and many old pools are not, then there is a potential for a shock from stray voltage.
once the cleaner is out of the pool I would call an electrician with pool experience. Tell them you have a stray voltage or bonding problem and ask if they have experience with those. It is probably a problem with the cleaner but it could be a sign of something more serious.
If you can't touch the cleaner or the pool without a shock even with the main off call an electrician or your power company now So Cal Edison? . You have a serious stray voltage problem.