If you need to interact with a rockcrab fishing spot, use the Npcs class, eg.
getNpcs().closest(fishing spot name or ID).interact("catch");
obv. with some added null checks and what have you. Interacting with an NPC will execute an InteractionEvent, which will walk to the npc as needed.
If you really just need to interact with a position ("RSTile"), you could do it by coordinates
new Position(x, y, z).interact(bot, "Walk here");
alternatively to walk to the position, use the Walking class, which has a number of methods that accept positions and areas.