Will renters insurance cover a in ground pool?

It depends on what you mean, Covered for what kind of loss?

Your renters insurance covers your personal property and certain of your liabilities to others, generally the owner of the rented property and your guests.

If you somehow accidentally damaged the pool in a home you rented then there may be coverage under the liability portion of your renters insurance policy.

If the pool suffered a weather related loss or damage from ground movement or another natural act then that would be covered under the property owners insurance policy. You don't own the pool, the landlord does and if you didn't break it then your not responsible for it beyond whatever agreed maintenance you were to perform.

If the pool just needs maintenance, cleaning, repair or servicing then no that's not covered at all as it is not considered a loss, it's just normal expected maintenance that all pools need.