At least 200 people are expected to take part in a triathlon in the Dengie.
The Big East Triathlon will be held on May 11 in Bradwell and the Dengie marshes.
Competitors can choose between two courses - a middle distance of 1.6km swim , 82km cycle and 20km run, or a challenge distance of 800m swim, 43km cycle and 10km run.
Alongside the triathlon, the Tour of the Dengie Cycle Ride will also taking place with a number of different distance options available.
At least 125 cyclists have registered to enter the ride, which is supported by British Cycling and will raise money for the Guide Dogs for the Blind Association.
Dengie Events has organised both sports challenges, which is open to complete beginners and experienced competitors. Visit dengieevents.co.uk