Incompatibilities/caveats:

This mod is not compatible with AAI Industries or Krastorio 2. They have special handling for offshore pumps that doesn't take into account the way that pumps can switch between inland and normal. The mod Pump Anywhere (https://mods.factorio.com/mod/PumpAnywhere) is an alternative with wider compatibility but without the option to require a technology to unlock the ability.

If the mod is uninstalled while inland pumps are unlocked, normal pumps will become inaccessible. To prevent this from happening, run the console command /inland-pumps-revert (does not disable achievements) before uninstalling the mod. To fix this once it has happened, reinstall the mod, run that command, and uninstall it, or run the console command /c for _, force in pairs(game.forces) do force.reset_technology_effects() end.

How it works:

Since I can't change where pumps can be placed while the game is running, I instead make a copy of each type of pump (modded ones included). When you unlock the ability to place pumps inland, it actually replaces all of the existing pumps with ones that let you place them inland, along with the recipes to create them. You can see it working when the mod text on the entities and recipes changes to "Inland Pumps".