I recall a couple cases like this in (fairly) recent memory.
I think one of them did end up passing away - not sure if it was still in the lake or thereafter.
Virgil the model husband had a young trotter end up in the lake at Northfield maybe..5-8 years ago that was retrieved and went on to race thereafter.
As you say, left to their own devices a horse will do fine in the water, but while harnessed and hooked, it is a bad scene.
Yeah, it's sad. I remember watching live & im pretty sure I remember a horse went over the rail & into the deep part of the centerfield pond & drowned.
Horse bad the bike attached & all the gear weighing him down, no chance.
If there is a pond, it should be no more than 3 feet deep.
I've also seen a horse get loose, do 5 laps on the half mile track with gear/bike attached, run down into the paddock, run out the entrance and right up the road, turned right and up another road and ended up getting stopped about a half mile away near a pharmacy.
Lucky it wasn't injured at all, scratched that day obv but raced a week later.