As with every Civilization expansion, Rising Tide adds an impressive amount of game-changing content. Not only did it overhaul the Diplomacy system and add aquatic floating cities, it also enhanced the exploration aspects by adding depth to Expeditions. The opening stages of the game are now much more competitive due to the faction boosting resources now available.
Explorer Units
Sending out Explorer units has always had benefits, as they can find Resource Pods with helpful caches of Culture, Science, Production, or Energy, or Orbital Units like Solar Collectors. You could also excavate a ruin site, sometimes getting an ancient Alien as a military unit. But the options now are much more vast, allowing the Explorers to perform Expeditions on abandoned stations, to progenitor ruins, to strange alien fungi and more. They’re also more abundant, meaning that you will need to produce Explorers long past the first third of the game, especially because Artifacts now come into play. There are a few Quest rewards and Virtue leafs that give your Explorer units the ability to go on more Expeditions. As this cuts down on the travel time needed for your Explorers to travel all the way back to your civilization to replenish their allotance, it is best that you use these as soon as you can in the game.
Another reason to build lots of Explorers is their new ability to Leash aliens. This not only helps avoid your unit being destroyed by a nearby hostile unit, but also allows you to build an army of aliens. This is a little less effective on an island based map, as land-based aliens cannot swim, but in wide open spaces can be used to your advantage, cutting out the time needed to build military units and compensating for the many Explorers units that will preoccupy your Production time. Ocean-based alien units can be leashed too, meaning you can build an alien navy.
Artifacts
The result of some of your expeditions will be Artifacts, which come in three types and a variety of conditions. You can get Artifacts that are either Old Earth, Alien, or Progenitor in origin. Combining them in your library can bring benefit to your faction in the form of Resources or technological rewards. If your Artifacts are in good enough condition, you can create an even better item that gives your civilization a huge boost, like increased Expedition speed or city health. The order in which they are placed and then combined in your library seems to play into the quality of your rewards, so save your game file first and test out the order before committing to the end result.