Since held items are enlarged when the player is underwater, maps (including buried treasure maps) held in one hand are not fully visible, making them difficult to use. This is not really an issue for other items.
Steps to Reproduce
Obtain a filled map of any kind.
Hold the map in the player’s hand (main or off-hand).
Stand above water and observe the map – it displays correctly.
Submerge fully underwater while still holding the map.
Observe the map’s appearance – it suddenly enlarges and extends off the screen.
Environment
Snapshot 25w37a
Overworld
Windows 11
Please edit your report to change the Affected Version to the version shown on the Minecraft title screen