Add more fish, water decorations and vegetation, boats for factions who use them, many types of horse carts and plows and eagles and the ability to ride them, unless it is already a thing. Also please add an extension of survival aspects of Minecraft like temperature and thirst. Also please a health system similiar to First Aid mod, it is really good.
These are a lot of features for one suggestion. Try to keep suggestions related to one subject.
The mod's being updated to 1.15, so it'll contain the new water features from the Aquatic Update.
More boats are planned for the future. 1.15 is already adding new boats for the mod's wood types.
Eagles are a planned feature.
The mod already adds a couple of new survival mechanics. Heat and cold damage in the Harad desert and Forodwaith respectively, for example. Hunger also decreases slower than in vanilla, due to the amount of travelling the mod requires.
I use cuchaz ships mod. This works very well except when you hit a fish or something else in the water. The fish move away from the boat so it doesn’t stay glitched. Lily pads and other aquatic plants are a different ballgame though, your boat freezes completely and you can’t destroy the lili pad. The only option is then to restart your game or spam backwards on the controls until you get out of the glitch. Even though there are fixes for this it is super annoying so avoid using these boats in rivers seeing as they often have plants, where as the ocean does not. Another problem is that every single one of the blocks that you need to turn a structure into a ship needs redstone and some need vanilla diamonds. This though, can be solved by going into creative and getting them or giving yourself the materials that are needed to craft the blocks.
The reason I prefer this over Archimedes though is that your boats do not need floaters anymore and they are so much more realistic. You can only craft them out of wood, and depending on the blocks on the boat it may be to heavy to float (this does not count blocks in chests). All boat require sails (except for the smallest ones, which move with a paddle) that require wool, the more sails or the bigger sails your boat has the faster it will go. Also you have the ability to leave the helm (the block that you use to steer the boat) and walk around while the boat is still moving. I said the ship can only be made out of wood but while this is true the ship can have other blocks placed on it. The thing is the ship blocks only recognize the wood blocks as part of the ship. The rest is cargo. NPCs can also sail on the ship making it so you can have a sort of navy with soldiers. Even though there are glitches this is hands down the best ship mod there is that fits in with the mod. As for the other features most of them are planned.