Boat and exit point
Stop the boat over the wreck and record the X/Z. Inspect the entrance from the surface, choose the way back without breaking the walls. For a short test, go down to the outer hole and immediately ascend: this way you can see whether there is enough air for the route itself. Reference: Minecraft: Ocean Monument.
Keep a potion of underwater breathing in your hotbar. For the base you need a rough potion and pufferfish, redstone prolongs the effect. Night vision improves visibility, but does not allow breathing.
Ship, ruins and treasure map
In the ship, look for accessible chests one at a time, do not try to go through all the compartments on the last bubbles. In the ocean ruins there are drowned ones, including trident throwers, and suspicious brush blocks.
The treasure map shows the red cross area, not the finished mine. Approach the mark, place the boat in a safe place and dig in layers with the exit up. The chest under the sand may require more time than the remaining air.
To make the necessary potions, use the following recipes: Brewing basics: the brewing stand and your first useful potions.
The monument is a separate expedition
elder guardian cast Mining Fatigue III, so breaking through the wall may take much longer. Milk removes Mining Fatigue along with underwater breathing and night vision - after it, restore the desired effects.
Magma bubble columns pull down, do not use them as a regular elevator to the air. For the first monument, prepare a stable supply point on the surface, several portions of potions and an escape route. Examination of an ordinary ship does not prove readiness for this battle.
Suspicious blocks are cleared according to separate instructions: Minecraft archaeology: brushes, suspicious blocks and safe digging.
