Go to page 2 for the dolphin discussion. :3
This is an in depth look at the secrets of the water in TF2.
The Disadvantages: You are slower underwater then on land, as a pyro almost all your guns are useless(shotgun and and excluded). You can drown if you stay under to long, you can use food items ie Sandvich, Bonk and Jarate. Huntsman wouldn't work underwater. When a cloaked spy leaves the water he with drip water reviling him for a short time.
The Advantages: You can fight in all 3 dimensions under(up down and so forth), You are harder to see underwater, people on the surface will not be able to see you as clearly as they would if you were on land. You can preform many sneak attacks and qiuck shots from the water, pyros can't attack you easily underwater as their best weapons are useless, you can remove fire and Jarate effects by jumping in the water, as a spy you can lose your attackers by going into the water.
The Strategies: Now that we have covered what can and can't be done will submerged in the water it is time for me to share some of my favorite underwater strategies. Most classes are good for fighting underwater, even the pyro is if you use him correctly. I will break down strategies by class for ease of access.
The Scout: Your fast and quick, so why not be underwater were most people are even slower then normal. The odds are in your favor. If you have the fan you can shoot your opponents around the water and disorient them or even shoot them out of the water for some seaworld esc tricks. The bat is a good weapon underwater beacuse when you can get under someone and smack them they have little chance to catch you. The odds are good for you winning underwater.
The Solider:Your slow but the water brings many classes to your speed, so use that to your advantage. Underwater fighting is hard for you but surface to water fighting will produce much better results. Your rockets will be able to hit targets directly from above and if you rocket jump above said water and hit some people on the way down you got some easy kills to clean up. If you happen to face someone faster then you underwater use the shotgun as the rocket launcher is slow to hit on land and slower underwater. The shovel crits often so if your right on them use it. Surface to water is your game.
The Pyro: Not the best place for you to be. But it is not a hopeless battle, your shotgun and axe will still be able to kill a target or two but don't stay in the water for long. If you feel you can fight underwater and your being chased jump in the water your attacker will most likely follow because he thinks the balls in his court and your done for but wait for him and smack him with your axe or shotgun. It is tough but don't give up hope.
The Demoman: It is not the best idea as most of your weapons are slow on land so they will not hit your targets to well, so surprise if the name of the game. Shoot some pipes up and hit a sentry without revealing your location. Or hit your opponents with your bottle it crits often enough to land you a kill. Not the best place but it has its ups.
The Heavy: Your really slow and underwater you might as well be going backward but the fight can still be yours. The minigun will kill most of your opponents because they have little places to run due to the large spread and if you have Natasha they will be slowed. You can take a lot of damage so use it to your advantage be like a submarine fighting a dolphin the dolphin may be faster but you are stronger and have better guns. Go for it by all means but be ready.
The Engineer: You can help make your team and a powerful underwater unit by building a dispenser and and a sentry. A teleporter if good as most people won't look for it there and it will get your team up and out quickly and safely. The dispenser will make sure everyone won't drown to death and keeps them supplied safely beacuse the sentry will take down most targets as the water is an open space. Great place to build and offensive base so get your scuba gear ready.
The Medic: You will want to fight someone here as you have the advantage of quickly hitting with the long range of your ubersaw. Always folow your teammates in and help them fight the long fight down there, your like an oxygen tank but make sure you can some for your self.
The Sniper: You are the best class for underwater fighting, most of the time the enemy will engage you long range just were you want them. Your sniper rifle will be the best thing to have for an underwater fight as the huntsman will not work underwater but dis pear not huntsman fans your strategy will come up later. The sub machine gun is good as it often crits and has a high rate of fire to make sure you hit your target. The Kukri crits all the time and is great for the quick smash and slash. The huntsman is good for your water to surface strikes as it take no time to power up. The Sniper Rifle can also do this job if you scope before you surface and make sure your on your target. They won't see it coming. Go for it mates it may be just what you need to turn that score around.
The Spy: You can use the water to lose your attackers and land strikes on new ones. With the cloak and dagger you can be invisible and submerged for long periods of time to strike an opponent from below. The best thing is to use the water to disguise and surface to make it look like you are on their team just swimming out of the base and hit them will a back stab when they are looking away.But remeber when you are cloaked and you surface onto land you will drip water.
So that is my in depth look on water, hope you enjoyed it and I still want some scuba gear.