This is a reaction.

ch3oh + o2 → co2 + 2h2o + heat

combustion

endothermic

substitution

spontaneous

Combustion. 
Anytime a reaction has CO2+2H2O, it's combustion

I’d have to say no because without oxygen in the water the fish would all be dead. so if you want to fish for dead fish, pick the ponds with the lowest oxygen concentrations.

Matter- occupies space and possesses rest massno matter is the opposite