This is an example of historical present, which is more common in Japanese than in English. Please see this for details. Here, present tense is used to describe what's happening in the video vividly. Something like this is especially common in sport news, so I think you can guess how it feels. I would not have been wrong at all to use the past tense consistently.

Note that ～てくる is not "future tense". This くる is simply describing the water is physically coming toward the river/camera. See this.

Regarding そこに, this そこ refers to "the current scene (calm river)", and this に is a direction/destination marker rather than a simple location marker. Here, そこに is an adverbial expression that describes something/someone entering the scene. I don't think this is a conjunction.

This is an example of historical present, which is more common in Japanese than in English. Please see this for details. Here, present tense is used to describe what's happening in the video vividly. Something like this is especially common in sport news, so I think you can guess how it feels. It would not have been wrong at all to use the past tense consistently.

Note that ～てくる is not "future tense". This くる is simply describing the water is physically coming toward the river/camera. See this.

Regarding そこに, this そこ refers to "the current scene (calm river)", and this に is a direction/destination marker rather than a simple location marker. Here, そこに is an adverbial expression that describes something/someone entering the scene. I don't think this is a conjunction.

This is an example of historical present, which is more common in Japanese than in English. Please see this for details. Here, present tense is used to describe what's happening in the video vividly. Something like this is especially common in sport news, so I think you can guess how it feels. It is not wrong at all to use the past tense consistently.

Note that ～てくる is not "future tense". Here this くる simply describes the water is coming toward the camera. See this.

Regarding そこに, そこ refers to ";this scene", and に is a direction/destination marker. It's an adverbial expression that describes something/someone entering the scene. I don't think this is a conjunction.

This is an example of historical present, which is more common in Japanese than in English. Please see this for details. Here, present tense is used to describe what's happening in the video vividly. Something like this is especially common in sport news, so I think you can guess how it feels. I would not have been wrong at all to use the past tense consistently.

Note that ～てくる is not "future tense". This くる is simply describing the water is physically coming toward the river/camera. See this.

Regarding そこに, this そこ refers to ";the current scene (calm river)", and this に is a direction/destination marker rather than a simple location marker. Here, そこに is an adverbial expression that describes something/someone entering the scene. I don't think this is a conjunction.