Sinised Lained (Blue Waves) has some great cruises on Pärnu Bay starting from 100€/1hr as well as yacht rentals with or without a hired captain if you have a boating licence. You can even set out to either Kihnu or Ruhnu islands for up to a few days. And don’t worry about any sort of Gilligan’s Island scenario happening, the captains are much more competent than the ‘Skipper’. It may be prudent to book something shorter or longer than a ‘3-hour tour’, however.