This short story I read at least 30 years ago, maybe more. Since I rarely read magazines it must have been in some collection but I don't remember anything about which one. So it could be older than that.
It is about a planet to where a first exploratory expedition had been sent and never came back. So a new one is sent, but knowing they must be extremely careful. The ship of the first one is readily found and shows that everyone has been dead almost since the time they had arrived. Somehow the new expedition has a brush with a huge creature which can kill, like an electric eel, by projecting an electric field (or maybe it was a magnetic field ?). Since they were on their guard, they manage to escape by the skin of their teeth and bring back the warning that this planet is really not fit for colonisation.