You can place frogspawn over boats on the water:
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Steps to Reproduce:
In a body of water spawn a boat
Stand over or generally above the boat
Crouch and use a frogspawn while aiming at the boat
Observed Behavior:
The frogspawn will place on top of the boat.
Expected Result:
Because the boat is the first targeted right-click interaction, when it fails (due to shift click being held), nothing would happen. The frog spawn would only be valid for placement if the player is directly targeting water.
Screenshots/Videos:
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Can confirm.