Deep sea boats - only for groups

If one of the goals is to encourage groups forming, a "deep sea boat" concept would go that way:

1) several size boats to be manned by different size groups:
-one-person rafts already exist
-2 and 3 person boats could be introduced to go out to sea.

2) "mini" sailing/rowing etc. game
the same way there are mini-games to gather resources, a group boat could have a mini game, but where different group members have different functions, at the same time (might be tricky in case one lags, but this concept can be broadened to other more general types of "group mini-games")
for instance:
-1 person steers (to avoid rocks etc)
-1/2 person manage sails/oars

3) group resource gathering
A "fishing net" could be introduced as part of the sailing/rowing minigame (e.g. the 3rd person throws the net), and several fish are caught so all members profit, or just the netcaster profit (to be investigated)
This could also be a separate minigame from the sailing/rowing minigame

4) islands
this group boat could be the only way to reach certain islands:
the 2-person boat can cross deep sea, while the 3-person boat can cross "very-deep" sea

5) sea maps
navigating / map drawing could be a new skill (or two different skills), and if you have a poor navigator or map drawer the progress is more random or not possible at all (especially in "deeper" sea / allowing a levelling concept).
You could be in a given square where an island is and never reach it if you don't have the appropriate map/ or if your navigating skill is too low.
The map drawer can then sell his map of a certain region of sea in the market to enable other people to reach given islands easier.

6) bonus in islands can be limited only by imagination
gold, monsters/boss, items, time cards (lol)...
but also quests (where you bring items from one place to another, or need to find someone etc, or need to gather or buy a type of resource, or craft something: like a seer but with more types of quests)

7) pirates
another type of mini game, or type of quest or whatever...

... other things come to mind: boatbuilding (in a group, with planks for hull and cloth for sails, or ...)