Well I hate the squirrels as much as anybody, they are worse than rats when it comes to mangoes, but its wise to be aware of the laws.
Catching a rodent in a box trap and putting the trap in the pond for drowning is effective but illegal - misdemeanor animal cruelty.
Relocation seems humane, but you have to be careful. For example, in California its strictly verboten.
https://www.discoverwildcare.org/wildlife-resources/trapping-and-relocating-wildlife/In Florida we have, in part:
Nuisance wildlife may only be released if:
1. The nuisance wildlife is released on the property of the landowner provided the release site and capture site are located on one contiguous piece of property, or
2. The nuisance wildlife is a native species; and,
3. The property where the nuisance animal is to be released is located within the county of capture and is a minimum of 40 contiguous acres; and,
4. The person releasing the nuisance wildlife is in possession, at time of release, of written permission from the property owner allowing such action.
Nuisance wildlife may not be released on federal, state, county, local or private lands without written permission of the landowner.
See:
https://myfwc.com/conservation/you-conserve/wildlife/relocate/and
https://www.flrules.org/gateway/RuleNo.asp?id=68A-9.010Don't want to see anyone get into trouble over these vermin.