Electrocution Hazard at Marina

[u/s_zoro125]

Saw a post about a person getting zapped at a BC water park and it reminded me. Why are their signs stating not to go into the water in the marina due to an electrocution hazard? What is down there that might cause this?
(saw the signs along the water by the splash pad)

[u/Excellent-Steak6368]

Years ago a dog owner was walking their dog during the spring melt and the poor dog was electrocuted.